
flass H Kaf g 



Copyright iN°J_9_lS- 



CDPYRIGHT DEPOSm 



DENTAL 
ELECTRO-THERAPEUTICS 



BY 
ERNEST STURRIDGE, L.D.S. (Eng.), D.D.S. 

FELLOW OF THE ROYAL SOCIETY OF MEDICINE, MEMBER OF THE BRITISH DENTAL ASSO- 
CIATION, MEMBER OF THE BRITISH SOCIETY FOR THE STUDY OF ORTHO- 
DONTICS, MEMBER OF THE AMERICAN DENTAL SOCIETY OF EUROPE, 
CONTRIBUTOR ON DENTAL ELECTRO-THERAPEUTICS IN "THE 
SCIENCE AND PRACTICE OF DENTAL SURGERY," ON 
IONIC MEDICATION IN PRINZ'S "DENTAL MATERIA 
MEDICA AND THERAPEUTICS." 



SECOND EDITION, THOROUGHLY REVISED 



ILLUSTRATED WITH 164 ENGRAVINGS 




LEA & FEBIGER 

PHILADELPHIA AND NEW YORK 
1918 






Copyright 

LEA & FEBIGER 

1918 



APR £C iS!3 

©CLA4946T4 






PREFACE TO THE SECOND EDITION. 



The kind reception accorded the first edition confirms the 
opinion expressed in the preface that there is urgent need 
for literature on dental electro-therapeutics. 

This edition has been thoroughly revised and brought up to 
date with the addition of some new matter and illustrations. 
The work is specially intended to bring forward the value of 
electro-sterilization in treatment of root canals and perio- 
dontal diseases, and this part has been rewritten with the 
intention of explaining more fully the technical details of 
ionization treatment. Details are given in respect to ratio 
of time required to current strength available in the electro- 
sterilization of hard and soft oral tissues, and I hope that 
this will be of value to those who are inexperienced in elec- 
trical treatment. I would repeat a word of warning to all 
who undertake this method of treatment: Do not approach 
the subject lightly; study carefully sufficient electro-physics 
to understand the various phenomena of the current with 
which you are dealing; and obtain a knowledge of the 
electro-physiological effects; then the therapeutic effects will 
be most gratifying. 

I gratefully acknowledge the assistance given by my 
friend Dr. C. H. Abbot who has revised the chapter on 
.T-ray technic and diagnosis, adding many useful hints to 
this part of the work. Best thanks are also accorded my 
daughter Miss Elsie Sturridge, L.D.S., R.C.S. (Eng.), for 
her valuable assistance in correcting proofs. 

E. S. 
London, 1918. 



CONTENTS. 

PART I. 
ELECTRO-PHYSICS. 



CHAPTER I. 



Frictional or Static Electricity. 

Theories as to the Nature of Electricity — Electroscope — Leyden Jar — ■ 

Conduction — Induction — Static Machine 17-27 



CHAPTER II. 

Galvanic Electricity. 

Volta's Contact Law — Electrolyte — Voltaic Cells — Electro-motive 
Force — Practical Electrical Units — Resistance — Heat Effect of the 
Current — Polarization — Poles — Testing the Poles — -Electrolysis — 
Ions — Electro-positive and Electro-negative 28-52 

CHAPTER III. 

Cells. 

Leclanche Wet and Dry Cells — Smee Cell — Bichromate of Potash Cell 
— Persulphate of Mercury Cell — Bunsen Cell — Grove Cell — - 
Daniell Cell — Secondary Batteries or Accumulators — Edison 
Storage Battery — Arrangement of Cells — Cells in Series — Cells in 
Parallel — Cells in Multiple Arc — Density 53-73 

CHAPTER IV. 

Magnetic Field, Dynamo Currents, and Batteries. 

Inducted Currents — Self-induction — Induction Coil — Secondary Coil 
— Continuous Current — Alternatin g Current — Transformers — 
Batteries — Home-made Battery — Cautery Battery — Accumula- 
tor Battery 74-97 



vi CONTENTS 

CHAPTER V. 

Batteey Accbssoeies. 

Current Collector — Milliamperemeter — Rheostats — Rheophores — 
Electrodes — Rheostat for Direct Current from the Main — -Resist- 
ance for Heavy Currents — Alternating Current Transformers — 
High-frequency Currents 98-122 

CHAPTER VI. 

Dental, Electrical Appliances. 

Motors — Electric Engines — Electric Lathes — Switchboards — Accumu- 
lators — Direct Resistance — Motor Converter — Electric Hot-air 
Syringe — Electric Sterilizer and Hot-water Apparatus — Foot 
Warmer — Electric Furnaces — Pyrometer — -Electric Cold An- 
nealer 123-136 

CHAPTER VII. 

The X-rays or Rontgen Rays. 

X-ray Apparatus — Dental Radiography — The Uses of the X-rays in 

Dentistry — Development of Radiographs 137-202 



PART II. 

ELECTRO-THERAPEUTICS. 

CHAPTER VIII. 

Electro-physiological Effects. 
General Considerations— Conduction by Ions 203-212 

CHAPTER IX. 

Physiological Effects of Currents. 

Cataphoric Effect — Electrolytic Effect — Path of the Current in the 
Body — Motor, Sensory and Special Nerve Effects — Effects of 
Current on Nutrition — Effects of Current on Salivary Glands — 
Resistance Effects of Current Passing through the Body . 213-230 



CONTENTS vii 

CHAPTER X. 

Electro-therapeutic Effects. 

Ionic Medication — From a Dental Aspect — The Zinc Ion — The 
Copper Ion — The Iodine Ion — The Silver Ion — The Cocaine Ion 
— The Adrenalin Ion — The Salicylic Ion — Advantages of Ionic 
Medication — Effects of Ions on Bacteria 231-249 

CHAPTER XI. 
Technic of Ionic Medication in Dental Operations . . 250-254 

CHAPTER XII. 

High-frequency and Static Currents. 
X-ray and High-frequency Currents 255-261 

CHAPTER XIII. 

Electro-therapeutics in Dentistry. 

Treatment of Root Canals — Periodontitis from Septic Pulp — Acute 
Local Periodontitis — Alveolar Abscess — Trismus from Impacted 
Third Molar — Chronic Alveolar Abscess — Perforation of the Root 
— Necrosis of the Jaws — Marginal Gingivitis 262-276 

CHAPTER XIV. 

Treatment of Pyorrhea Alveolaris. 

Periodontal Disease — Incipient Infection of the Gingival Trough — 
Septic Infection of Gingival Trough without Suppuration — 
Septic Infection of Periodontal Membrane — Acute Septic Infec- 
tion of Gums and Periodontal Membrane — Chronic Septic Perio- 
dontal Disease 277-299 

CHAPTER XV. 

Electricity for Anesthesia, for Bleaching, and for Neuralgia. 

Anesthesia of Sensitive Dentine — For Immediate Extirpation — Anes- 
thesia of Gums and Alveolus — Electric Tooth Bleaching — Bleach- 
ing with Chlorinated Lime — Bleaching with Hydrogen Dioxide 
—Neuralgia 300-314 



DENTAL ELECTRO-THERAPEUTICS. 



PART I. 

ELECTRO-PHYSICS 



CHAPTER I. 
FRICTIONAL OR STATIC ELECTRICITY. 

Theories as to the Nature of Electricity— Electroscope — Ley den Jar — 
Conduction — Induction — Static Machine. 

The study of electrical science embraces a wide and 
varied field. Many of the phenomena are well known and 
are placed on sure and scientific footing. Hypotheses have 
been suggested by eminent modern works in physics which 
connect electricity with "the ether" in a way comparable 
with light and heat. 

The manifestations of electricity with which we have 
most to do from a dental aspect are those of energy, force, 
and power, and in order to understand how these are brought 
about, and how they can be utilized, the study of electricity 
should be undertaken from the very primitive forms of 
electrical phenomena which have been known for ages to 
the very latest discoveries of the effect of the current from 
a therapeutic stand -point. 

A primitive electrical phenomenon was observed by 

early workers in the science, who noted that when certain 

substances are rubbed together a current of electricity is 

generated which is possessed of certain definite properties. 

2 



18 FR1CT10NAL OR STATIC ELECTRICITY 

The character of the current and the effect produced 
depend on the method of exciting it and the substance used. 

From these early experiments in the production of electric 
current, methods have gradually developed into the present- 
day elaborate plans for the production of electricity. 

It is said that Greek philosophers, many hundred years 
B.C., noted that when amber was rubbed with cloth it had 
the power of attracting other bodies, but it was Dr. Gilbert, 
of Colchester, an Englishman, who in the later part of the six- 
teenth century, made a study of this phenomenon, and who 
by experiments determined which bodies would and which 
would not acquire the property. He also gave the name 
of Electricity to the cause of this attraction. He tested 
substances by bringing them near a metal needle, lightly 
balanced on a pivot. 

If we rub a glass rod with silk, or a piece of sealing wax 
with flannel, the friction will excite electricity in the rubbed 
end of glass or wax, and if we apply them to some light 
substances, such as scraps of paper or a suspended pith 
ball, we shall find that they will attract these bodies. 

If we suspend a ball of elder-pith by a silk thread attached 
to the end of a ruler and apply the piece of silk, which has 
been used to rub the glass rod, we shall find that the pith 
ball will be repelled. It is clear that there are two forces 
excited, the one on the glass rod which attracts, and the 
other on the silk which repels the pith ball. The sub- 
stances which have been rubbed have always contained 
electricity, and although the one attracts and the other 
repels the pith ball, it is not that there are two kinds of 
electricity, but only two degrees of the same current; in 
other words, there is a difference of power or potential. 
The approach of the glass rod to the pith ball alters the 
balance of electricity in the ball by inducing a current on 
the side nearest the rod of opposite sign to that on the rod, 
the farther side is charged with current of the same sign as 
that on the rod. 

"Bodies charged with unlike electricities attract one 
another and bodies charged with like electricities repel," or 



THEORIES AS TO NATURE OF ELECTRICITY 19 

in the light of recent research, the current from the body 
which is more highly charged, tends to flow toward that 
in which there is a deficiency of charge, or away from that 
in which there is already a charge; in other words, there 
tends to be a levelling up. 

The term positive (+) electricity is applied to current 
of greater power, and negative ( — ) electricity to the lesser, 
the differences are only potential, quantity, direction of flow, 
and rate of variation of these. 

Metals do not become perceptibly electrified when rubbed 
with other substances in the same way as glass or sealing 
wax, because they possess the power of conducting electricity; 
friction fails to disturb the balance of electricity in a sub- 
stance which so conveys electricity, a good conductor, as it 
is called, because any disturbance is promptly neutralized 
by the electricity flowing back to the point from which it was 
displaced. 

Electricity may also pass from one substance in Avhich 
it has been excited to another which has affinity for it, 
without actually being brought in contact with it; that is, 
it may pass through an intervening air space and charge 
another body, or a currect of opposite sign may be excited 
in a body brought near a charged body, from which it is 
insulated. This effect is brought about by induction 
(see p. 24). 

Theories as to the Nature of Electricity. — A theory was 
propounded by Robert Symmer in 1789 which is generally 
known as the two-fluid theory, in which it is advocated 
that every body contains an unlimited store of electric 
fluid of two opposite kinds which neutralize one another, 
being of equal amounts, the positive and negative kinds. 
These two electric fluids, he assumed, are capable of being 
divided, when they are excited by friction or otherwise, 
and the body which contained the greater amount of fluid 
is positively electrified, and that which contains the lesser 
negatively electrified. This hypothesis, which, whether 
regarded as true or not, possesses an analogous bearing on 
facts which frequently must be referred to. 



20 FRICTIONAL OR STATIC ELECTRICITY 

Another theory which was suggested by Sir William 
Watson in 1747, and further elaborated on by Benjamin 
Franklin, is that there is but one kind of electricity, that 
when the current is excited or set in motion by friction or 
otherwise, one body becomes possessed of more current 
than the other at the expense of the other, the former being 
positively and the latter negatively electrified. This theory 
is often referred to as the one-fluid theory. Other views on 
electricity may be obtained from such authors as Green, 
Stokes, Maxwell, and Oliver Lodge. 

The latest theory is that propounded by Prof. J. J. 
Thomson, of Cambridge, at the beginning of the present 
century. "According to this, electricity is regarded not 
as a fluid, but yet as having real existence in the form of 
minute fragments called Electrons. Definite information 
has been obtained as to the size, etc., of only one kind of 
electron, that which conveys negative electricity. It is 
possible that positive electrons also exist. These negative 
electrons can exist alone : when in motion they form an elec- 
tric current. They can become attached to the atoms of a 
solid body, and the body is then negatively charged. Each 
atom of an ordinary solid body is supposed to contain 
many such negative electrons, paired off with an equal 
number of positive electrons, and if any of these negative 
electrons are torn away the body is left positively charged. 

"The process by which a metal conducts electricity 
probably consists in the passing of electrons from one 
immovable molecule in the solid body to the molecule next 
to it. The mass of each of these electrons is the same, and 
only about j^q of that of the lightest atom known (that 
of hydrogen)." This concise explanation of the electron 
theory is taken from C. E. Ashford's Electricity and 
Magnetism . 

The Electroscope. — We have noted that electricity of 
unlike kinds generated by friction attracts, and that of like 
kinds repels each other. To tell when a body is electrified, 
and which kind of electricity it is charged with, the electro- 
scope is an easy means. 



THE LEY DEN JAR 



21 




Fig. 1.— Electro- 
scope. 



There are many forms and modifications of the electro- 
scope. One of the simplest is the gold-leaf electroscope. 
This consists of a vessel in which is suspended by a metal 
wire two strips of gold-leaf placed slightly 
apart. The wire is connected to a brass 
rod, which passes through the center of the 
cork in the jar and terminates in a metal 
plate or knob. If we approach the knob 
of the electroscope with a glass rod, which 
has been charged with positive electricity 
the charge will pass to the gold-leaf, both 
strips become positively charged and repel 
each other. Similarly, if a negatively 
charged substance be applied to the un- 
charged electroscope, the gold-leaf will be 
repelled. If the electroscope be affected 
by a charged body whose sign we desire 
to determine by bringing in contact an 
electrified glass rod, if it be positively 
charged the gold-leaf will diverge still farther, but if 
negatively charged the gold-leaf will collapse. The glass 
rod used to test the electroscope will lose none of its 
electrification, and on removing it the gold-leaf will relapse 
into its former position. 

This sensitive instrument will determine if a body is only 
slightly charged with electricity; if the gold-leaf diverge 
ever so little the body is charged. 

The Leyden Jar. — This is a convenient form of condenser 
and collector of electricity. It is usually constructed of a 
glass jar lined with tin-foil on the inside to within a few 
inches of the top, and similarly coated on the outside. 
Through the cork is passed a brass rod which terminates 
externally in a knob, and after going more than half-way 
into the jar, terminates in a brass chain resting on the 
metallic lining of the bottom of the jar. The foil lining 
the inside and coating the outside constitutes the two 
conductors, the glass intervening, the dielectric of the 
condenser. 



22 



FRICTION AL OR STATIC ELECTRICITY 




Fig. 2. — Ley den 
jar. 



To charge the jar the knob is connected with the con- 
ductor of a working frictional machine, and the outer 
coat is connected with earth, the charge passing to the 
inner coating of the jar acts on the outer 
coating through the intervening dielectric by 
induction. This induced current is conveyed 
away to earth, leaving a charge of opposite 
sign held there by the charge on the inner 
coat. This increases the "capacity" of the 
inner coat. 

To discharge the jar it is only necessary 
to bring a conductor which is in contact 
with the outer coat near to the knob of the 
jar, when a spark will occur by the coming 
together of the two electricities, thus estab- 
lishing equilibrium. 

The quantity of electricity which the con- 
denser will contain depends on the surface 
area of the metallic lining and the strength of the dielectric. 
If the Leyden jar is made of very thin glass, and a charge 
of very high potential passed into it, it is liable to be broken 
by the strain and a spark passes. 

The phenomenon of the discharge of the Leyden jar, 
which takes place with sudden oscillations and a spark, 
enters into the principle of the construction of many 
appliances made for electrical treatment. The capacity of 
the jar varies with the area of the conducting surfaces and 
the thickness of the dielectric. If the area is large and the 
dielectric thin, the capacity will be greater than if the 
dielectric is thick with the same area — that is, the capacity 
of the jar is greatly increased if the area is increased and 
the dielectric remains the same thickness. 

Conduction. — The conduction of electricity up to a point 
resembles that of heat, especially when we think of it as 
being conveyed along a metal. In whatever way an electric 
current moves it certainly is transferred from point to 
point by a certain class of substances, which when they 
permit of the free passing of electricity are known as 



CONDUCTION 23 

conductors, while other substances, which only allow of 
very little passing or apparently no passing of current are 
called non-conductors. If the gold-leaf of the electroscope 
be suspended by glass or vulcanite or some such substance 
known as a non-conductor, no current would pass, not that 
these substances do not contain electricity, because it has 
been shown that it may be excited on them. On the other 
hand, if a metal be rubbed and applied to the sensitive 
electroscope it will be found to have no effect on the gold- 
leaf, because, though current is generated, it is conducted 
away. A comparative list of substances which are good, 
poor, and non-conductors of electricity can be readily 
compiled. Metals and carbon come under the head of 
good conductors; silver, copper, platinum, iron, zinc, and 
mercury are the best. Poor conductors include water, 
saline solutions, acid solutions, the body, etc. Non-con- 
ductors include glass, vulcanite, paraffin, sealing-wax, dry 
skin, dry air, etc. Every conceivable thing might be in- 
cluded under one of these heads, those mentioned come 
most frequently under our notice. There is a certain 
amount of resistance offered to the passing of electricity 
even by the very best conductors, the comparison of the 
conductors depends entirely on this property of resistance, 
but even those substances known as insulators convey a 
certain amount of current. (The amount they allow to 
pass in some instances becomes dependent on the electrical 
force which repels the current.) 

During conduction of electricity, heat is always generated. 
This property depends on the amount of current which is 
passing and the resistance which is present. 

From the foregoing it may be concluded that there is 
no demarcation between conductors and insulators. All 
substances may be accounted conductors, but some con- 
duct so badly that they are termed non-conductors. Even 
these are at times affected by their physical state. The 
skin, for example, when perfectly dry is a very poor con- 
ductor, but when moistened is a fairly good conductor. 
Inversely, good conductors are similarly affected by their 



24 FRICTION AL OR STATIC ELECTRICITY 

physical state. Metals when heated become poorer con- 
ductors, whereas heat increases the conductivity of carbon. 
Pure water does not conduct, but acidulated water, or 
water to which is added a small quantity of salt becomes a 
good conductor. The reason for these effects of the physical 
state on the conductivity of current will be referred to later. 
The conduction of electricity through gases should not be 
lost sight of, for it has a bearing on the action of the 
current in passing through certain vacuum tubes like the 
.r-ray tube. 

Induction. — It has been stated that all bodies more or 
less contain electricity, which if it is not manifest, one 
reason is that it is evenly distributed, and that it may be 
excited and made manifest in different ways. The glass 
rod, for example, contains electricity, which can be excited 
by rubbing with silk. If the electrified glass rod is brought 
near to a suspended insulated pith ball it will attract it. 
The explanation of this is that the positively electrified 
body brought in proximity of the body which contains a 
certain amount of electricity evenly distributed over its 
surface, causes an alteration in the distribution of elec- 
tricity by inducing negative electricity to the surface nearest 
to the charged rod, and as unlike attracts, the light body is 
drawn toward the electrified rod. Induction takes place 
whenever an electrified body is brought near another body. 
If an insulated substance is touched by the electrified body 
it will become charged with electricity of the like sign, 
but if the electrified body be removed without touching, 
the distribution of electricity in the other becomes once 
more evenly dispersed over its surface. If the insulated 
body instead of being round be pointed at each end, and 
another insulated positively electrified body be brought 
near one end, it will induce current of a negative sign to 
the point, where the density will become so great, that if 
they are brought close enough a discharge across the inter- 
vening space in a spark will take place, neutralizing the 
electrified body and leaving itself charged with electricity 
of the opposite sign. 



STATIC MACHINES 25 

Static Machines. — The current produced by frictional 
machines is the most ancient form of procuring a continuous 
current of electricity for therapeutic purposes. One older 
type of machine was constructed on the principle of generat- 
ing a current by friction of a revolving glass cylinder with 
an amalgamated leather rubber. The negative electricity 
generated on the rubber is conducted to earth with the aid 
of the amalgam, and the positive electricity on the glass 
attracts a negative charge from a stationary metallic prime 
conductor placed in close proximity. A negative charge from 
the prime conductor neutralizes the positive charged glass 
cylinder, and retains a charge of positive electricity, which 
can be conducted from the prime conductor. This form of 
machine has been superseded by improved induction or 
influence machines. One type, long known and used, is the 
Holtz machine, which, with the many modern improve- 
ments, is still very popular. In this country the Wimshurst 
machine seems to be preferred. It has the advantages 
of being self-exciting, and does not reverse the current 
generated under climatic influences while in action. "It 
consists of two circular glass disks (or any even number), 
mounted in pairs upon a fixed horizontal spindle in such a 
way that they rotate in opposite directions at a distance 
apart of not more than a fraction of an inch. Each disk is 
attached to the end of a hollow boss of wood, or of metal, 
upon which is turned a small pulley. The pulleys are 
driven by a cord or belt from larger pulleys attached to a 
spindle below the machine, and rotated by a winch handle 
or by a motor, the differences in the direction of rotation 
of the disks being obtained by crossing the alternating belts. 
Both disks are well varnished, and attached to the outer 
surface of each of these are radial sector-shaped plates of 
tin-foil or thin brass disposed around the disks at equal 
angles. These sectors are not essential to the action of the 
machine but they make it more easily self-exciting. 

"Twice in each revolution the two sectors situated on 
the same diameter of each disk are momentarily placed in 
metallic connection with one another by a pair of fixed 



26 



FRICTION AL OR STATIC ELECTRICITY 



wire brushes attached to the ends of a curved rod, called 
the neutralizing rod, supported at the middle of its length 
by one of the projecting ends of the fixed spindle upon 
which the disks rotate, the sector-shaped plates just grazing 
the tips of the brushes as they pass them. 




Fig. 3. — Wimshurst machine. 



" The position of the two pairs of brushes with respect to 
the fixed collecting combs and to one another is variable, 
as each pair is capable of being rotated on the spindle 
through a certain angle, and there is one position of maxi- 
mum efficiency. This position in the machine appears to 



STATIC MACHINES 2? 

be when the brushes touch the disks on diameters situated 
about 75° from the collecting combs, and 30° from one 
another. 

"The fixed conductors consist of two forks furnished with 
collecting combs directed toward one another, and toward 
the two disks which rotate between them, the position of 
the two forks, which are supported on ebonite pillars, being 
along the horizontal diameter of the disks. To these fixed 
conductors are attached the terminal electrodes, whose 
distance apart can be varied. Leyden jars are usually 
fitted to the machine by the makers, but these must admit 
of their outer coating being disconnected, if the machine is 
to be used for treating patients." 1 There are many modifica- 
tions of the Wimshurst machine, some having ebonite 
plates, others mica disks. These substances permit of 
driving the machine at a high speed without fear of breaking 
the plates. All, however, are made on the principle of the 
above description of a frictional machine here quoted. 

1 Lewis Jones: Medical electricity. 



CHAPTER II. 
GALVANIC ELECTRICITY 

Volta's Contact Law — Electrolyte — Voltaic Cells — Electro-motive Force 
— Practical Electrical Units — Resistance — Heat Effect of the Current — 
Polarization — Poles — - Testing the Poles — Electrolysis — Ions — Electro- 
positive and Electro-negative. 

Galvanic electricity is generated by galvanic or voltaic 
cells and by dynamos. It is the form of current which is 
most used in electro-therapeutics. Its force and current- 
strength can be graduated and controlled at will. This 
form of current is universally in use in the world's commerce, 
for which purpose it is generated by dynamos. Thus it is 
often termed Dynamic Electricity. 

Discovered by Galvani in 1780 and improved in method 
of production by Volta in 1800, it often bears the names of 
these eminent students. 

Galvanic electricity is produced when two dissimilar con- 
ductors are immersed in a liquid medium, called an elec- 
trolyte, which has the power of acting chemically on one 
of them more than the other — the metals being joined 
outside the liquid; that is, a circuit is formed, and the 
current will flow between the two metals within the fluid 
and be conducted along the plates and connecting wire. 

It is necessary to dwell upon and study the foregoing 
statement that two dissimilar substances are required to 
form a current-producing cell. 

If the metals or plates of a cell are exactly alike or even 
very similar and are immersed into a fluid electrolyte, which 
is capable of acting chemically upon them, no electric 
current will be produced; for example, if two zinc plates or 
two copper plates are placed in a solution of weak sulphuric 



VOLTA'S CONTACT LAW 29 

acid and the plates connected without by wires, on testing 
the wires connecting these similar plates no current will 
be found to pass, but if a zinc plate and a copper plate 
are immersed in a similar acid solution and connected by 
copper wire a strong electric current will immediately flow 
from the zinc to the copper within the solution and then 
along the copper plate and copper wire connection without 
in a continuous circuit. 

Electrolytic conduction only occurs by chemical action, 
as will subsequently be explained, and it is necessary that 
the metals or conductors employed must have different 
affinities for oxygen. This law is observed in the construction 
of all galvanic cells. 

The potential or electro-motive force depends on the 
amount of chemical action of the electrolyte on the sub- 
stances employed, and this potential difference is governed 
by the dissimilarity in the chemical affinities of the plates 
employed. If, for instance, platinum and copper be brought 
together in a cell, the copper would become positively 
electrified and the platinum negatively, and the current 
produced by such a cell would be feeble compared to one 
composed of zinc and copper, both of which are oxidizable, 
the zinc in this case being more highly so becomes positively 
electrified and the copper negatively; the potential of the 
current from this cell is much greater than the other. 

Zinc is one of the most oxidizable metals and most easily 
acted upon by electrolytes. It is therefore much used in 
the formation of voltaic cells. Copper, carbon, and silver 
are very dissimilar to zinc and are often used as negative 
elements in the construction of cells where zinc is the positive 
element. 

Volta's Contact Law. — To Volta is due the discovery of 
the manifestation of difference in potential by contact of 
dissimilar metals in air, and also, as is known in the con- 
struction of cells, that the size or form of the metals does 
not affect the potential, but only their dissimilarity and the 
nature of the metals employed. The electro-motive force 
which can be obtained by bringing together two metals in 



30 GALVANIC ELECTRICITY 

an electrolyte varies as the degree to which one becomes 
electro-positive and the other electro-negative when in 
contact. 

Lists have been arranged according to Volta's contact 
list, in which each substance or metal in the list will be 
positively electrified when in contact with any metal suc- 
ceeding it, and vice versa, negatively electrified in contact 
with any metal preceding it on the list. In the list the farther 
removed from one another in the series the greater will be 
the electro-faction of the metals if brought together in con- 
tact; thus zinc and carbon will have a potential difference 
far greater than zinc and iron. 

Such a contact series is as follows: 

Sodium. Copper. 

Zinc. Silver. 

Iron. Gold. 

Lead. Platinum. 

Tin. Carbon. 

According to Volta's contact law, "The difference of 
potential between any two metals is equal to the sum of the 
difference of the potential between the intervening metals 
in the contact series." 

In the construction of galvanic or voltaic cells the metal 
plates are usually chosen with due respect to their differ- 
ence of potential, but other properties have also to be taken 
into account, e. g., sodium is never used, although between it 
and carbon there is one of the highest potential differences, 
because it would not be manageable for a battery. 

The Electrolyte. — The electrolyte of a cell is the excitant 
and conductor of current. It acts chemically on the two 
elements and conveys electrically charged atoms from one 
to the other when the circuit is closed. 

Among the commoner fluids used as electrolytes in gal- 
vanic cells are dilute sulphuric acid, ammonium chloride, 
persulphate of mercury, etc. 

Voltaic Cells. — To construct a voltaic or galvanic cell, 
select any two of the dissimilar metals from the foregoing 



ELECTRO-MO TI VE FORCE 



31 



>n 






e^s 



Fig. 4. — Voltaic cell. 



contact series, the one farthest removed from one another 
will be the most highly electrified when placed in an electro- 
lyte, which has a greater chemical action on one than the 
other. Take zinc and copper for the elements, and sulphuric 
acid; immerse the two metals in the acid, connect the 
ends outside the vessel with wires (see 
Fig. 4). As soon as the contact is made 
a continuous current will flow from the 
zinc through the liquid to the copper; 
this is the stronger current set up by 
establishing a potential difference be- 
tween the two elements — that is, elec- 
trifying one element positively and the 
other negatively. The positive ( + ) 
electricity on reaching the opposite ele- 
ment is conducted by it to the wire 
connection without the cell, and con- 
veyed back to the zinc again through 
the electrolyte, making a complete circuit, which will go on 
until the electrolytic strain on the higher potential is reduced 
to equilibrium by the ceasing of chemical action of the 
electrolyte on the elements, either by their destruction 
or by the conversion of the oxidizable surface through the 
deposit of some chemical product of a less electrostatic nature. 

The actual passing of current through the conducting 
fluid is effected by the splitting of the H 2 molecules, by 
the electrolytic effect of the current into hydrogen and 
oxygen atoms — ions, i. e., atoms carrying electrical charges. 
The hydrogen ions are charged with positive electricity, 
and move toward the copper, where they give up their charge 
of positive electricity to the metal and hydrogen is liberated. 
At the same time the oxygen ions move toward the zinc where 
they give up their charge of negative electricity, and oxygen 
is liberated or unites chemically with the metal. 

Electro-motive Force (E. M. P.). — When electricity is 
excited by the proximity of two dissimilar metals in an 
electrolyte, or by dynamos or by whatever means produced, 
that force which sets the current in motion, that which 



32 GALVANIC ELECTRICITY 

separates the positive from the negative current is called 
electro-motive force (E. M. F.). 

It is that pressure or potential of the current between 
the positive and negative poles, which always flows from 
the positive to the negative pole and will continue in that 
direction until equilibrium of pressure or potential is estab- 
lished. "It is that which produces, or tends to produce, 
movement of electricity." 1 

The analogy of the flow of electric current to that of the 
flow of water is often made in text-books, the difference in 
the level of the water being used in the stead of the difference 
in the potential of electricity, the point being there must 
always be a difference of pressure or potential in order to 
have a flow, and the greater the pressure the greater is the 
flow. In thinking of this analogy of pressure resembling 
the flow of water from a higher to a lower level, the thought 
of the lesser current must not be eliminated, for one kind of 
current cannot flow continuously without the other. 

E. M. F. when applied to a conductor like metal propels 
continuously irrespective of altitudes or position, from the 
greater to the lesser potential ; when applied to an electrolyte, 
it is also continuous from the positive to the negative. 

The earth is always electrically charged, but there is a 
balance of potential between the positive and the negative 
electricity. The earth's potential is less than any current 
in motion, and consequently electricity in motion is always 
directed toward it. If we touch an electric motor lathe or 
the terminals of a switchboard, which are electrically con- 
nected with current from the main, and at the same time 
make contact with a gas or water pipe, which is in good 
contact with earth, the current from the high potential 
electrical source will be conducted through the body to 
earth, producing a disagreeable shock. 

In the construction of voltaic cells the electro-motive 
force varies, and depends not on the size of the cell, but on 
the dissimilarity of the metals or "plates" which enter into 

1 Ashford: Electricity and Magnetism. 



ELECTRO-MOTIVE FORCE 33 

their formation. The degree to which one metal becomes 
more highly electrified than the other, and that tendency 
of the current produced between the metals in a conducting 
fluid to move from the higher to the lower potential 
establishes the electro-motive force of the cell. 

The electro-motive force can be measured according to 
Ohm's law, by ascertaining the resistance and the current 
strength and multiplying them together. 

E = CR 
where . . . jE7 is the electromotive force 

C is the current strength 
and . . . R is the resistance 

If we know any two of these factors we can calculate the 
third thus : 

If the resistance of a cell and the resistance of the external 
circuit are together 1000 ohms and the current strength is 
0.001 ampere (1 milliampere), 

1000 ohms X 0.001 ampere = 1 volt E. M. F. 

in this way we ascertain that the E. M. F. of the cell is 
1 volt. 

The current, the E. M. F., and the resistance can be 
measured by suitable instruments, which will be described 
in another chapter. 

It has been stated that the E. M. F. of a cell depends on 
the plates which enter into its formation, and reference has 
been made to the "volt," but it has not been pointed out 
what the volt is. Different cells, according to the fore- 
going, vary in the E. M. F., and we require some standard 
with which to compare the E. M. F. of cells. 1 u The most 
natural thing to do is to take some cell, which can easily 
be set up, as having unit E. M. F. But there is a certain 
E. M. F. which depends on the fundamental units, the 
centimeter, the gramme, and the second, together with the 
magnetic action of a current of electricity, and it is most 

1 This is quoted from Ashford's Electricity and Magnetism. 
3 



34 GALVANIC ELECTRICITY 

convenient to take this, or some simple multiple of it, as 
the unit of E. M. F. The name given to the practical unit 
of E. M. F. is the volt, in honor of Volta. 

" Unfortunately, no cell has exactly this theoretical E. M. 
F., but by careful experiments it has been found that a 
certain cell, called Latimer Clark's Standard, if made up 
accurately to a certain specification and measured at a 
temperature of 15° C. has an E. M. F. equal to 1.434 of 
these theoretical volts. 

"This cell, then, can be used as a standard, just as con- 
veniently as if it had an E. M. F. of 1 volt; other cells can 
be compared with it, and their E. M. F. calculated." 

Practical Electrical Units. — The system of measurements 
of electrical units is based on the scientific calculation which 
is known as the absolute system. This starts by taking the 
unit of length, the meter, as a definite fraction of the earth's 
circumference. The unit of surface is obtained from this. 
For the unit of weight a smaller quantity is wanted, and the 
unit employed is the weight of a cubic centimeter (1 cubic 
meter = 1,000,000 cubic centimeters) of pure water at 4° C. 
(the temperature at which it possesses its greatest density 
as it expands again between 4° and 0° C. For the unit of 
mass the gramme, and for the unit of time the second or the 
centimeter-gramme-second (C. G. S.) system. 

The units with which we are most concerned are the 
Ohm, Volt, Ampere, Coulomb, Farad, and Watt, and these 
are all based on the C. G. S. system. 

The Ohm is the unit of resistance (R). It represents the 
measurement of whatever opposes the passing of current in 
any circuit. In calculating resistance to current produced 
by a voltaic cell the resistance opposed in circuit outside the 
cell (whether it is only the wires connecting the elements or 
whether it is a body in circuit) is estimated as external 
resistance (R) and is added to the resistance which is offered 
to passing of current from one element to the other through 
the electrolyte within the cell and through the ('lenient itself 
and termed internal resistance (r). 

The ohm is the resistance offered by a column of pure 



ELECTRO-MOTIVE FORCE 35 

mercury 106 cm. high and 1 sq. mm. cross-section at a 
temperature of 0° C. 

Resistance varies in different conductors; iron wire, for 
example, has about six times the resistance of copper wire. 

The Volt (V) is the practical unit for electro-motive force. 
It is the pressure that will cause the current flowing through 
1 ohm of resistance to be 1 ampere. 

The electro-motive force of the Daniell cell is sometimes 
used as the standard unit. It is about 1.079 volts, but 
varies with variations in concentration of the solutions used, 
and is consequently not as good a standard to go by as the 
Latimer Clark's cell (see p. 34), but the Daniell cell is one 
of the best-known two-fluid cells and is often referred to as 
the standard unit cell producing about 1 volt electro-motive 
force. 

The Ampere is the unit of current strength (C). It repre- 
sents the current which is furnished by an electro-motive 
force of 1 volt passing through a resistance of 1 ohm. This 
amount or quantity of current strength is far in excess of 
what is required in electro-therapeutics. It is therefore 
further divided into one thousandth of an ampere and 
termed the milliampere (0.001 ampere). 

The Coulomb is the unit of quantity. One coulomb is 
the quantity of current which flows past any point in a 
circuit of one ampere current strength for one second. 

In calculating the quantity of current which discharges 
from accumulators the term ampere-hour is used, which 
indicates the quantity of current which will be carried by 
one ampere in one hour. 

"The standard value of the coulomb is equivalent to 
the quantity of electricity that will flow through or into a 
body when a current-strength of 1 ampere is maintained 
for one second," 1 i. e., if we are passing a current of 5 milli- 
amperes through a patient for 20 minutes the number of 
coulombs that have been applied is 

0.005 X 20 X 60 - 6. 
1 Dawson Turner: Practical Medical Electricity. 



36 GALVANIC ELECTRICITY 

The Farad is the unit of capacity. It is that capacity 
which would require 1 coulomb to charge it to 1 volt. A 
condenser which is of a given capacity must contain a given 
area of metallic conductor lining to charge it to the potential 
of 1 volt. 

The Watt is the unit of electric power. It is the volt- 
ampere. A current of 1 ampere with a potential of 1 volt 
has a power of 1 watt, or a proportionately smaller current 
strength and greater electro-motive force will produce the 
same power; for example, T V ampere and 10 volts will pro- 
duce one watt. The number of watts is determined by multi- 
plying the number of amperes by the volts. 736 watts 
are equal to one horse-power. 

Resistance. — It has been stated that conductivity of 
electricity by solids varies greatly with the nature of the 
material. Resistance may be said to be the inverse to 
conduction. Metals are accounted the best conductors, 
but however good the conductors an amount of resistance 
is encountered on the passing of electric current. The 
amount of resistance varies according to the kind of con- 
ductor, the nature of the material has an influence on the 
resistance; certain pure metals, which offer least resistance 
to current are changed by being alloyed. Copper, for 
instance, offers little resistance to current, but when alloyed 
to form German silver (copper 60 parts, zinc 26, nickel 14) 
has a high resistance. 

The resistance varies directly as the length and inversely 
as the square of the diameter. 

A metal wire of a given length has twice the resistance of 
a similar wire of half that length; so, too, if the diameter 
of a given length of a conductor be increased by twice, the 
resistance will be reduced to one-quarter the other. 

The resistance of metal conductors is therefore dependent 
in individual cases on the nature of the material, the length, 
and diameter. 

With the exception of a few alloys, raising the temperature 
increases the resistance of metals; the resistance of carbon 
is decreased with raising the temperature. 



RESISTANCE 37 

A table of resistance of metals in comparison of a similar 
length and thickness would work out as follows: 

Sflver 1.00 

Copper 1.06 

Gold 1.38 

Aluminium . .1.94 

Platinum 6.08 

Iron 6.80 

Lead 13.60 

Mercury 62.50 

If the resistance of a given length of silver wire of a given 
thickness be ascertained, the resistance of any of the others 
may be calculated from this table. 

The conduction of liquids excepting mercury is, as has 
been explained, of quite a different nature; some are almost 
non-conductors of current, as oils for instance. 

In passing a current through a liquid resistance, as in 
the electrolyte of a cell, decomposition takes place. The 
body comes under the heading of liquid conductors, and 
various tissues and liquids in its composition have a greatly 
varying resistance. 

To calculate the resistance the current meets in an electric 
circuit derived from a cell, the internal resistance, that is, 
resistance met chiefly in the electrolyte within the cell 
between the exciting plates, must be taken into account 
and added to the external resistance, which is the resistance 
met in the metallic conducting wires, and whatever body 
is interposed between the two terminals or poles. 

To calculate resistance, current strength and electro-motive 
force it is necessary to have a clear conception of the law 
laid down by Ohm, which deals with the relation of force 
or potential to current strength and resistance. 

Omrs Law. — "The strength of the current in any circuit 
or part of a circuit A~aries directly as the electro-motive 
force in that circuit, and inversely as the resistance of the 
circuit." 

To clearly understand this law examples of its equations 
explain it more fully. 



38 GALVANIC ELECTRICITY 

Let E stand for electro-motive force in volts, C for current 
strength in amperes, and II for resistance in ohms. 

E 

Current strength = ^7" 

Electro-motive force = CR 
E 
Resistance = ~^ 

From these equations it is easy to calculate C, E, or R 
by a simple algebraic sum. To find the current strength 
(C) when E. M. F. is known to be 18 volts and R 1500 
ohms: 

18 
C = — ' = 0.012 (ampere) = 12 milliamperes. 
1500 

To find electro-motive force when R is 2000 ohms and 
C is 0.008 ampere : 

E = 0.008 X 2000 = 16 volts. 

To find resistance when E is 18 volts and C is 0.006 
ampere : 

R = — - = 3000 ohms. 
0.006 

The practical application of Ohm's law contributes to 
our proper understanding of much we have to study in 
electro-physics. In practice much interest is added to our 
electro-therapeutics by calculating the resistance of different 
patients, and it will be found, if this is done, that resistance 
of the body varies in a remarkable manner in different 
patients. 

Heat Effect of the Current.— One of the effects by which 
the presence of current can be ascertained in passing through 
a conductor is the heat produced. The amount of heat 
produced may not be sufficient appreciably to raise the 
temperature, but if the current is sufficiently large and 
resistance high enough, in time the temperature of the con- 



HEAT EFFECT OF THE CURRENT 39 

ductor will be raised to appreciable heat or even red or 
white heat. The quantity of heat produced by the passing 
of a definite current through a definite resistance in a given 
time has been calculated by Joub, who formulated a law 
which says that "the number of units of heat generated 
by a current in a conductor is proportional (1) to its resis- 
tance, (2) to the square of the strength of the current, 
(3) to the time during which it flows." From this law can 
be calculated the quantity of heat produced when a given 
current flows through a circuit with a given resistance in a 
given time. The energy absorbed by the resistance of the 
circuit is dissipated in the form of heat. The energy utilized 
in the production of heat is dependent on the resistance 
of the conductor. Thus when we want to produce great 
heat, as in a cautery, a strong current strength is passed 
through a small area and length of platinum wire which 
affords a great deal of resistance. If a good conducting 
wire like silver is used, the resistance of which is one-sixth 
that of platinum, a much greater current strength will be 
required to heat the wire to redness. The part resistance 
plays in respect to energy in the production of heat when 
a current is passed through different conductors may be 
amplified by the experiment of passing a current through 
a small chain consisting of alternate links of platinum and 
silver; when the current is sufficient to produce red heat 
in the platinum links the silver links will remain unheated 
perceptibly. 

The resistance of the filament of an incandescent lamp has 
to be great, and the production of light is in consequence 
of the raising of the temperature to white heat in a vacuum, 
the resistance required and the current employed being 
dependent on the E. M. F. and the candle power of the 
lamp. 

The heating properties of the current passing through a 
wire of small dimensions and known resistance has been 
utilized in construction of hot-wire instruments for the meas- 
urement of alternating and high-frequency currents, where 
magnetic instruments would be useless. Milliampere meters 



40 GALVANIC ELECTRICITY 

are constructed for this purpose on the principle of heating; 
by the passage of the current a fine platinum wire is heated 
and by expansion caused a pointer attached is rotated over 
a scale which indicates the current. 

In the practical use of the current the heating effect 
can be noticed when the author's method of bleaching 
dead teeth is carried out. If two fine platinum wires are 
inserted at two points in the dentine and the bleaching 
agent interposed as the conductor and completer of the 
circuit, when current strength of over 10 milliamperes is 
passing, the whole structure of the crown of the tooth 
becomes perceptibly heated, and if the current strength is 
raised for a minute or two to 15 milliamperes the heat 
becomes intolerable to the patient. 

One of the effects of general electrization by high-frequency 
currents is the production of heat, an increase of the surface 
temperature of the body frequently takes place and the 
patient feels warm. 

D' Arson val has shown that under the influence of auto- 
conduction the heat given off from the body is greatly 
increased. 

Polarization. — This term is applied to an obstructing of the 
current in chemically formed cells and has to be reckoned 
with in considering the resistance to current within the 
cell. It is brought about by an alteration of the surface of 
the plates of the cell during the chemical action which 
excites the flow of current, usually by the accumulation of 
hydrogen gas on the negative plate. Take, for example, a 
simple galvanic cell composed of zinc and silver with an 
electrolyte of ammonium chloride; on closing the circuit 
electricity flows within the cell from the zinc to the silver 
and electrolysis takes place, the hydrogen ions pass to the 
silver plate, discharge their current to the conducting metal, 
and hydrogen gas accumulates on the surface of the plate 
which it coats with bubbles. These bubbles act as a buffer 
or resistance to further electrolytic action. At the same 
time oxygen ions migrate to the zinc plate, discharge their 
electric charge, and act chemically on the zinc to form 



POLES 41 

oxide of zinc. The polarization of the silver plate by the 
coating of hydrogen bubbles on its surface changes that 
element from one of dissimilarity to the zinc to practically 
one of great similarity ; the relative potential is altered. This 
is opposed to Volta's contact law, which says that in order 
to produce flow of current it is necessary to connect two 
dissimilar elements in an electrolyte. 

To overcome polarization in cells, makers devise different 
methods to eliminate the gases or neutralize the chemical 
product which accumulates on the plates during the work- 
ing of the cells. This is called depolarization. It may be 
accomplished to a certain extent by mechanical means, 
but the method most commonly used is the introduction 
of some chemical which by its affinity for the polarizing 
product unites with it to form some other product which 
does not affect the action of the cell, and rids the plates 
of the polarizing effect. The depolarizer lessens the internal 
resistance of the cell, which would increase as the current 
continued to flow and the E. M. F. would gradually fall. 
Hydrogen gas on the negative element is the most frequent 
polarizing product of a cell and the method of depolarizing 
is generally a chemical one, by the presence of some oxidiz- 
ing agent which unites with the hydrogen as fast as it appears 
on the surface of the plates. In the Leclanche cell, manga- 
nese peroxide is the depolarizer; in bichromate of potash 
cell, chromic acid; in the persulphate of mercury, persulphate 
of mercury. 

Poles. — In all chemical cells the flow of current is from 
the positive (+) element to the negative ( — ) within the 
cell; that is, from the greater potential to the lesser, but it 
must not be forgotten that there is also a weaker current 
which flows in the opposite direction from ( — ) to (+). 
When the current of higher potential (+) passing through 
the electrolyte reaches the negative ( — ) element it is con- 
ducted by it outside the cell to the end which is called the 
terminal; therefore the negative element without the cell 
becomes the positive pole, because it conveys the current 
of higher potential, and the positive element becomes the 



42 



GALVANIC ELECTRICITY 



negative pole. A study of the accompanying illustration 
will serve to explain how the current flowing in a closed 
circuit from a cell has the + pole at the terminal of the 
negative element. 

Testing the Poles. — The chemical action at the + 
pole in a circuit is acid and at the — pole alkaline; that is, 
when current flows through a liquid separating the terminal 
in the circuit. Many simple tests which are useful in deter- 
mining the poles are based on the acidity and alkalinity of 
the respective poles. 




Fig. 5. — Direction of current inside and outside cell. 

To find the poles: 1. Moisten a slip of blue litmus and 
place it on a glass slab, apply the electrodes conveying 
current from two poles of a battery or whatever source of 
electricity, about 3 cm. apart, the paper will turn red at 
the + pole. 

2. A few drops of phenolphthalein (a clear, colorless 
liquid) in a glass of water and two metal electrodes placed 
3 or 4 cm. apart in the water, with a current in circuit, will 
give a bright purple coloring to the water about the — 
electrode. The commonly employed testing paper is paper 
impregnated with this solution. 

3. A simple and convenient method is to immerse the 
wires from the terminals of the cell in water containing a 



ELECTROLYSIS 43 

little salt or acid ; a few small bubbles collect on the positive 
pole and tend to stick to it and grow larger, while a number 
of minute bubbles collect on the negative pole and tend to 
leave it rapidly and rise to the surface of the liquid. 

One of these tests is often a handy means of determining 
the poles when dealing with current from, the main, in 
using a switchboard, even though the poles are marked; 
the plug connecting the board may become reversed and 
the identity of the poles lost. A milliampere meter attached 
to a switchboard is always an indicator of the constancy 
of the poles; if the plug is reversed the current in passing 
through the instrument will deflect the needle in the opposite 
direction to that marked on the terminal on the board, 
indicating the change in direction of the flow of current. 

Electrolysis. — It has been pointed out that when two dis- 
similar elements are connected in an electrolyte or exciting 
fluid, a current flows from the positive to the negative ele- 
ment within the cell and that a chemical action takes place 
within the cell. 

A similar chemical action takes place when current 
collected from a cell or other source of electricity is passed 
through a liquid or compound or tissue outside a cell or 
other electrical source of current supply between the two 
terminals. 

If we place two platinum electrodes in a vessel contain- 
ing water and pass a current through the water, bubbles 
of gas will rise from each electrode which will be found to 
be oxygen at the positive and hydrogen at the negative 
electrode, the formation of these gases would take place 
exceedingly slowly, hardly at all, because pure water is 
almost a non-conductor of current, and is only mentioned 
here as an example of the splitting of a liquid by the action 
of the current. 

Electrolysis may be defined as "the process of splitting 
up a liquid chemically by passing an electric current through 
it." The liquid is the electrolyte, the positive electrode is 
called the anode and the negative electrode the kathode. 

Now if the water in the foregoing experiment contains 



44 GALVANIC ELECTRICITY 

a salt in solution it becomes a good conductor of electricity 
and the electrolytic action is greatly increased. The action 
of the current on a large class of compounds dissolved in 
water or other solvent may be explained by taking one of 
the simplest salts, sodium chloride (NaCl) for example, 
which in the solid state consists of molecules composed of 
one atom of sodium and one of chloride, when dissolved 
in water a certain number of the molecules dissociate into 
atoms of sodium and chlorine, these atoms move about in 
the solution in no regular formation and with no particular 
destiny, and are the ions when electricity is passed through 
the solution. 

The effect of the current on such a solution is to cause 
decomposition of the solution (or electrolyte), the molecule 
NaCl is split or dissociated into the ion Na, which becomes 
positively charged and the ion CI which becomes negatively 
charged. The charge of current is equal in each case. The 
positively charged ion moves toward the negative electrode 
and the negatively charged ion toward the positive electrode. 
In this manner electric current passes through the electro- 
lyte, the ions conveying definite charges of electricity, 
and oxygen is liberated at the anode and hydrogen at the 
kathode. 

But in the case of an electrolyte containing a salt and 
an alkali metal, the action is often far more complicated; 
it may be found that when the molecule is split one of the 
electrically charged atoms is composed of a chemical com- 
pound of an unknown composition, in which case the atom 
may combine with one of the atoms of water to form a new 
chemical compound. 

Take, for example, copper sulphate, CuS0 4 , if this is 
electrolyzed between platinum electrodes, the Cu ion moves 
to the kathode and copper is deposited on the platinum 
and hydrogen is liberated, the S0 4 ion (which is called sulph- 
ion, but is not a chemical compound) moves to the anode, 
where it unites with some of the water (H 2 0) to form sul- 
phuric acid (H 2 S0 4 ) and oxygen is liberated. 

If the same salt is electrolyzed between copper electrodes 



ELECTROLYSIS 45 

there is a further effect produced, another reaction takes 
place, the sulphion (S0 4 ) instead of uniting with the H 2 
atom of water, attacks the copper anode and forms copper 
sulphate (CuS0 4 ) after giving up its charge of electricity 
to the electrode, and the metal is in the course of time 
reduced in weight by the loss of copper ions which go into 
the electrolyte and replenishes it. At the same time the 
copper ion (Cu) is deposited on the cathode after giving 
up its charge of electricity, and this electrode is increased 
in weight at the expense of the other. 

If sodium sulphate (XaS0 4 ) is electrolyzed between 
platinum electrodes a still further effect will be produced. 
There will be a secondary action at both electrodes. The 
following action takes place, the sodium sulphate is split 
into sodium and sulphion, the sodium (Xa) ions become 
positively charged and move toward the kathode, where 
the electric charge is given up and the sodium unites with 
hydrogen of the water, forming sodium hydrate and liber- 
ating hydrogen; the sulphion (S0 4 ) becomes negatively 
charged and moves toward the anode, where the electric 
charge is given up and sulphion (S0 4 ) unites with the water 
(H 2 0) to form sulphuric acid (H 2 S0 4 ) and oxygen (0) is 
liberated. If to this solution some neutral litmus is added 
before electrolyzing it a blue reaction will appear at the 
kathode and red at the anode, indicating alkalinity at the 
kathode and acidity at the anode. 

The quantitative results of electrolysis were determined 
by Faraday, who by experiments discovered the relative 
quantities of substances liberated at the electrodes. He 
found that when the current is passed through a series of 
voltameters (or electrolytic cells) with the same electro- 
lytes and the same electrodes that the weight of the product 
of electrolysis in each cell was the same, but when the 
electrolytes and the electrodes were different the product of 
electrolysis varied according to the chemical equivalent 
quantities; he therefore formulated the law: "When a 
current passes through different electrolytes in series the ratio 
between the quantities of the substances appearing at the elec- 



46 GALVANIC ELECTRICITY 

trodes is the same as that of their chemical equivalents" A 
simple but clear explanation of this law is here quoted from 
Ashford as follows: "Suppose that a current passes through 
two cells in series containing respectively (A) acidulated 
water, (B) copper sulphate solution, both with platinum 
electrodes, and a third (C) containing copper sulphate 
solution with copper electrodes. Suppose that the current 
is allowed to flow until 1 gram of hydrogen has been liber- 
ated in A. To form the water in A, 8 grams of copper are 
combined with each gram of hydrogen, so that 8 grams of 
oxygen are liberated at the anode in A, and therefore also 
at the anode at B. Now 31.7 grams of copper are chemi- 
cally equivalent to 8 grams of oxygen so that 31.7 grams 
of copper will be deposited on the cathode in B and there- 
fore also in C. Thus from Faraday's results we see that the 
following quantities are simultaneously liberated: Hydrogen 
1, oxygen 8, copper 31.7. These numbers are the chemical 
equivalents of these elements." 

Ions. — In the section on Electrolysis it was stated that 
the action of the current in an electrolyte is to split it up 
chemically into simpler materials which move to their 
respective electrodes. The term ions is given to these 
materials; that which travels to the anode is called the 
anion, that which goes to the kathode the kation. (The 
terms anion and kation although often used in reference to 
ionization are very misleading and difficult to construe and 
will be seldom used here, to avoid confusion.) 

The ion is the conveyer of electricity. It is the product 
of a splitting up of the component parts of a compound 
and is associated with the idea of something which moves or 
is going in some direction. 

Salts are formed by the chemical union of metals or 
metallic radicals with acid radicals; when a current is passed 
through an electrolyte containing a salt in solution, the 
metals or metallic radicals move from the anode to the kathode 
(hydrogen is included in these) and the acid radicals always 
move in the opposite direction, i. e.,from the kathode to the 
anode. Those atoms which are split by the electrolytic 



IONS 47 

action of the current are the ions which carry definite charges 
of electricity and are set free at the respective electrodes 
to which they migrate. In the case of acids in the compo- 
sition of an electrolyte they act like salts whose metal is 
hydrogen; thus in hydrochloric acid, hydrogen will appear 
at the kathode and chlorine at the anode. 

Bases act like salts whose acid is hydroxyl (OH). Thus 
in potassium hydrate (KOH) the (K) potassium becomes 
positively charged and will appear at the kathode and the 
(OH) hydroxyl becomes negatively charged and will appear 
at the anode. 

Leduc in explaining the migration of ions says: "The 
fragments resulting from the dissociation of molecules are 
the ions, and these ions are carriers of electric charges, to 
which the electrolytic conduction is due. The anions carry 
negative charges, and are consequently attracted by the 
positive electricity of the anode. The kations carry posi- 
tive charges: they are repelled by the anode and attracted 
by the negative electricity in contact with the kathode. 
On coming in contact with the electrode, the ions are 
unloaded, neutralizing quantities of electricity equal to, 
and of opposite sign to themselves; and these quantities 
of electricity will be replaced by new charges coming from 
the generator, and it is thus that the electric current is 
produced and maintained. 

"Plurovalent ions carry electric charges proportioned to 
their valency; or rather it is the electric charges which 
determine the valency." 1 

The rate of movement of ions in an electrolyte varies 
according to the electro-motive force and the direction of 
migration of the ions, those conveying positive charges 
moving faster than the negatively charged ions. "Hottorf 
has shown that the velocity of anions differs from that of 
kations. This may be proved by the following experiment: 
A solution of sulphate of copper is placed in an electrolyte 
cell with a porous partition, the solution being identical 

1 Leduc: Electric Ions and Their Use in Medicine. 



48 GALVANIC ELECTRICITY 

on both sides of the partition. After passing a current 
for some time the solution is found to be more concentrated 
on one side of the partition. The anion S0 4 has travelled 
faster than the kation Cu, although the number of ions 
liberated at the electrodes is the same 



SO4SO4SO4 ! SO4SO4SO4 I 
Cu Cu Cu Cu Cu Cu I + 



Before the passage of current. 

S0 4 [ SO4 SO4 SO4 S0 4 S0 4 I 
- j Cu CuCuCu I Cu Cu + 

After the passage of current. 

"The ratio of the degree of concentration on either side 
of the porous diaphragm enables us to estimate the relative 
velocities of the anions and kations respectively." 1 

This experiment is also alluded to by Leduc, who points 
out that "Three ions are liberated at each electrode, but 
in consequence of the difference of the speed of the ions 
the negative half of the cell does not contain more than 
one molecule of sulphate of copper, having lost two-thirds 
of its concentration, while the positive half contains two 
parts, having lost only one-third of its concentration. It is 
easy to conclude from this that the ions move in opposite 
directions at different rates." 

The rate of travel and the depth of penetration of ion 
when the electrolyte is a moistened tissue depends in a 
measure on the current strength and resistance offered in 
the particular tissue; that is, the molecular conductivity 
of the kind of electrolyte will influence the passing of ions, 
and this must be considered in their practical application; 
a liquid will convey ions at a rapid rate with little resistance, 
whereas gelatinous substances or a tissue will retard the 
rate of travel. The kind of tissue, whether a good electro- 
lyte or an indifferent one, will influence the speed and pene- 
tration of ions. The penetration will also be considerably 

1 Guilleminot: Electricity in Medicine. 



IONS 49 

affected by the changes the ions undergo when they enter 
the tissue. Some are precipitated at once and only remain 
in the superficial layers, while others can be driven in to a 
great depth. 

A simple ionic effect is furnished when the current is 
passed through an aqueous solution of zinc chloride, the 
zinc chloride molecules are dissociated by the effect on the 
solution, zinc ions charged with positive electricity migrate 
toward the negative electrode while the CI ions become 
charged with negative electricity and migrate in the opposite 
directions. 

A practical but more complicated illustration is found 
in gold plating, a process carried out in most dental labora- 
tories. Here the electrolyte is cyanide of gold (8 KCX 
+ 4 Au + 2 + 2H 2 0), the positive electrode is a piece of 
pure gold (anode), the negative electrode is the piece to be 
plated (kathode), which may be gold, silver, copper, German 
silver, etc. By the electrolytic effect the solution is split 
into Au ions charged with positive electricity, which migrate 
toward the negative electrode to which they give up their 
charge of positive electricity and on which gold is deposited, 
at the same time the dissociated KCX ions migrate toward 
the positive electrode (gold) where they give up their 
charge of negative electricity, and here one of the compli- 
cated electrolytic effects takes place. The KCX atoms 
unite chemically with 2 and the gold electrode to form 
gold cyanide which replenishes the solution with gold 
atoms. The atoms in the charged state are supposed to 
take on a regular formation and to migrate to their respec- 
tive directions (Fig. 6). The velocity of migration of the 
gold ions varies with the drop in voltage and consequently 
with the current strength and also with the temperature 
of the electrolyte. If we desire to plate a piece with a 
thick coating of gold we use a strong current with a solution 
rich in gold ions and raise the temperature slightly. 

The gas bubbles which collect at the electrodes are H 2 
at the kathode and O at the anode, which are ions of the 
molecule H 2 charged, dissociated, and migrated in precisely 

4 



50 



GALVANIC ELECTRICITY 



the same manner as the other ions of this compound 
solution. 

Electro-positive and Electro-negative. — From the 
foregoing it has been pointed out that the action of the 
current on molecules of salts in solution is to split up the 
component parts into ions, which become positively and 
negatively charged and move in the direction of attraction 
of the particular ion, or, in another sense, to be repelled from 
one pole toward the other. The ions, which are positively 
charged, are repelled from the positive pole and carry a 
positive charge of current with them, these are termed 



Battery 




Fig. 



-The supposed migration of ions. 



electro-positive. Those which are negatively charged are 
repelled from the negative pole and are called electro-negative. 
An example of electro-positive and electro-negative 
elements in an electrolyte-conducting current is often ex- 
perienced in the mouths of patients whose approximating 
surface of teeth are filled with two dissimilar metals; take, 
for instance, two premolars, the posterior approximal surface 
of the first filled with amalgam and the anterior approx- 
imal surface of the second filled with gold, both fillings ex- 
tending to the cervical margin, the secretions of the mouth 
provide an excellent electrolyte. In these cases if the metals 



IONS 51 

are slightly in contact at the articulating surfaces of the 
fillings a perfect cell is formed and current strength which 
is produced by such a cell is considerable — quite sufficient 
to cause considerable pain if the pulps are alive. It is likely 
that E. M. F. in such a cell is sufficient to produce a cur- 
rent strength of one or more milliamperes. The author 
has tested fillings of this description and found that the 
discomfort complained of from the electric current pro- 
duced by their proximity was greater than that produced 
by passing one milliampere of current through the fillings 
from a galvanic generator. According to Volta's Contact 
Law, amalgam in this tiny cell is positively charged and 
gold negatively, therefore the direction of flow of current 
when the circuit is closed is from the amalgam to the gold 
through the electrolyte, and ions conveying electric charges 
are electro-positive from the amalgam to the gold and 
electro-negative ions from the gold to the amalgam. These 
may consist of ions of any salt present. There are many 
medical solvents which are neither electro-positive nor 
electro-negative, that is, they do not permit of separation 
of ions, even when they contain those salts which in an elec- 
trolyte are readily dissociated. 

Among these are alcohol, glycerine, vaseline, chloroform, 
ether, and oils. These are nearly all included in a list given 
by J. H. Morton, 1 of New York, of substances which are 
stated by him to be acted upon or conveyed by electric 
osmosis or cataphoresis. 

There are many substances with which we frequently 
deal in electro-therapeutics that are formed by the union 
of metallic radicals with acid radicals; such compounds are 
sodium chloride, zinc chloride, copper sulphate, etc., which 
when acted upon by an electric current separate into electro- 
positive and electro-negative ions. The direction of migra- 
tion of ions contained in a salt must be known in order 
to determine the proper poles to apply to medicate with 
the ions desired. For example, if zinc ions are required 
from, zinc chloride and the negative electrode be applied 

1 Cataphoresis, p. 144. 



52 GALVANIC ELECTRICITY 

to the site of medication, chlorine gas would be liberated 
without any migration of zinc ions. 

All acid radicals are negatively charged and all basic 
radicals positively. The following are a few electro-chemical 
substances arranged under the headings of 



Electro-positive. 
Hydrogen. 
Mercury. 
Copper. 
Iron. 


Electro-negative, 
Oxygen. 
Nitrogen. 
Sulphur. 
Chlorine. 


Zinc. 


Bromine. 


Sodium. 


Iodine. 


Potassium. 


Arsenic. 



By the foregoing it is clear that when a current is passed 
in a circuit through an electrolyte containing a salt in 
solution the dissociation of the component parts takes 
place, the ions formed convey the electrical charges positive 
or negative in opposite directions to the conducting elec- 
trodes, where they give up their charges. When they have 
lost their charges they reunite by the laws of chemistry 
with the elements in the electrolyte for which they have 
affinities. For instance, if sodium chloride is the salt and 
saliva the electrolyte in the cell referred to of amalgam and 
gold fillings between the teeth, when the Na ions conveying 
their charges of electricity reach the gold conductor they 
lose their charges and the Na unites chemically with OH 
(Na + H 2 0. = NaOH + H) in the saliva to form NaOH. 
The CI ions likewise lose their charges to the amalgam and 
the CI unites chemically with the metal, tending to destroy 
it. These chemical changes take place at the electric ele- 
ments of all batteries or cells, and it may reasonably be 
conjectured that this chemical change taking place in the 
instance of fillings of dissimilar metals between the teeth 
may be the cause of rapid disintegration of inorganic salts 
at the marginal edge of the fillings, when this product of 
electrolysis is an acid. Or, conversely, may be the means 
of preserving the marginal edges in the case of the product 
being an alkaline or antiseptic. 



CHAPTER III. 
CELLS. 

Leclanche Wet and Dry Cells — Smee Cell — Bichromate of Potash Cell — 
Persulphate of Mercury Cell — Bunsen Cell — Grove Cell — Daniell Cell — 
Secondary Batteries or Accumulators — Edison Storage Battery — Arrange- 
ment of Cells — Cells in Series — Cells in Parallel — Cells in Multiple Arc — ■ 
Density. 

One of the important sources of supply of electric current 
for dental purposes is from cells. The principle of con- 
struction of a voltaic cell has been described on page 30. 
In the manufacture of cells, makers observe strictly the 
laws which govern the generation of galvanic currents, 
Volta's Contact Law, resistance, polarization, and depolari- 
zation. A constant and efficient supply of current from a 
cell depends on a combination of adaptability of the plates 
to these laws, the chemical action of the electrolyte employed, 
and the difficult question of polarization and depolarization. 

Leclanche Wet Cell. — Of the many forms of primary cells 
the one which is most useful is the Leclanche cell. The 
Leclanche cell consists (1) of a glass jar in which is placed 
a porous pot containing in the centre a carbon rod sur- 
rounded by coarsely powdered carbon and peroxide of 
manganese, this forms the negative element; (2) a rod of 
amalgamated zinc, which forms the positive element; (3) 
the electrolyte consisting of a strong solution of ammo- 
nium chloride (sal ammoniac) . These constitute the internal 
arrangements of the cell. The carbon is electro-negative 
and very dissimilar to zinc, which is electro-positive. The 
electrolyte ammonium chloride (2XH 4 C1) acts chemically on 
the zinc to form zinc chloride (ZnCl 2 ) ammonia (2XH 3 ) and 
hydrogen (H 2 ). 

Zn + 2NH 4 C1 = ZnCl 2 + 2NH 3 + H 2 



54 



CELLS 



By the action of the current generated when the circuit is 
closed, within the cell the ion NH 4 migrates to the negative 
element, and the ion CI migrates to the positive element, 
conveying their respective charges of electricity which they 
unload to the conductor elements. The chlorine atom 
unites with the zinc to form zinc chloride; the ammonia is 
soluble in water and is dissolved in the electrolyte solution 
at the negative (carbon), the hydrogen collects on the nega- 
tive element in the form of gas bubbles and causes polariza- 
tion, but the carbon rod is surrounded with peroxide of 
manganese which is rich in oxygen, the 
hydrogen bubbles unite with the oxy- 
gen to form water, and by this means 
depolarization is effected. When the 
circuit is closed (that is, the elements 
connected outside the cell by a conduct- 
ing wire) the cell gradually weakens, 
the polarization of the cell takes place 
faster than the depolarization, and 
the flow of current gets gradually 
less. 

This kind of cell, however, has the 
property of recovering rapidly when the 
circuit is again broken, the manganese 
— WetLeeianchS dioxide continues its action of depolari- 
ceii. zation until the cell is free from the 

collection of hydrogen gas on the nega- 
tive element. The chemical action of this cell ceases when 
the circuit is broken, so that its elements are not continually 
acted upon and it is a most lasting and economical cell. 

A collection of these cells makes a very useful battery 
for dental purposes, if kept in a cabinet and the water and 
ammonium chloride renewed when required, will remain 
active for a number of years, requiring very little attention. 
The zincs are destroyed in time by chemical action but 
they are readily replaced. When it is unnecessary to move 
the battery about, as is the case in a dental surgery, these 
cells are admirably adapted. 




LECLAXCHE DRY CELL 



oo 



The electro-motive force (E) of the Leclanche cell is 
1.47 volts; there is considerable internal resistance (r). 
The calculation of the current strength (c) can be readily 
carried out according to Ohm's law. It will be found that 
one cell is inadequate for dental purposes with the body in 
circuit. 

Take, for example, the resistance of 1500 ohms for the 
body and roughly 0.25 ohm for internal resistance. The 
equation then is : 



1.47 V 



R1500 + 0.25r 



= 0.001 ampere = 1 millianipere 



It is therefore necessary to collect the current from a 
number of these cells by joining them in series in the form 
of a battery. 

Leclanche Dry Cell. — This cell is made on the same prin- 
ciple as the wet cell described. Instead of the glass jar, the 
case of the cell is made of zinc which is used as the positive 
element; in the centre is the carbon nega- 
tive element surrounded with a layer of 
manganese dioxide as the depolarizer. 
The electrolyte is a pasty substance com- 
posed of some preparation of ammonium 
chloride. The cell is sealed at the top 
and is of small size, the smallest measur- 
ing If x 1J x 3f inches. The current 
produced by one of these small cells is 
about equal to a wet cell of ordinary 
size and it will last a fairly long time. 
Internal resistance of the Leclanche cell 
is a factor in its construction, for which 
makers have devised several methods to 
overcome. Messrs. Schall & Son make 
one form which they supply in their 
batteries in which zinc is placed inside a cylinder of carbon, 
separated from it by the electrolyte. 

The advantages of the Leclanche dry cell over the wet 




Fig. 8. — Leclanche 
dry cell. 



56 CELLS 

are that they are encased in metal and are unbreakable; 
they contain no liquid which would be liable to spill, they 
are sealed, and there is no corroding of the terminals, the 
internal resistance is slightly less and E. M. F. slightly 
greater than the ordinary wet cell. 

The principal disadvantage they possess is that they 
cannot be recharged, when used up they become worthless, 
but they last long enough to make this disadvantage hardly 
worthy of mention. Two years in constant use in a dental 
practice might well be the life of a dry cell. 

The Smee Cell. — This is a simple cell made of plates of 
amalgamated zinc to form the positive element. These 
are placed parallel to each other and separated by a plate 
of silver coated with a thin layer of platinum to form the 
negative element. These two metals, zinc and platinum, are 
far apart in the contact series and the electro-motive force 
generated is greater than it would be if the negative plates 
were made of either silver or copper, platinum being more 
electro-negative to zinc than either silver or copper. The 
electrolyte consists of a weak solution of sulphuric acid. 
There is no chemical depolarizer in this cell, the depolariza- 
tion is mechanical, that is, the gas bubbles are unable to 
cling to the surface of the platinum plate and the plate 
keeps comparatively clear of this polarizing agent, but it 
is an imperfect means of depolarizing. 

The zinc of the cell must be withdrawn when the current 
is not being used, for the constant chemical action of the 
acid on the zinc destroys it. 

The electro-motive force of the cell is about 2 volts and 
when in use it is rapidly reduced on account of the collec- 
tion of hydrogen gas which collects on the negative plate. 
This type of cell has been much used in the past for electro- 
therapeutic purposes, but for dental work it has no advantage 
over the Leclanche cell. 

Bichromate of Potash Cell. — This cell is constructed of a 
plate of zinc which forms the positive element, and two 
plates of carbon set one on either side of the zinc which 
form the negative element. The electrolyte is dilute sul- 



PERSULPHATE OF MERCURY CELL 



57 




phuric acid. A mixture of strong sulphuric acid, powdered 
bichromate of potash and water is the depolarizer. The 
electrolyte is sometimes varied by the use of chromic acid 
instead of potash, because its chemical action lessens the 
internal resistance. The chemical action of the cell is con- 
stant and the metal element is arranged so that it can be 
removed from the electrolyte when 
the cell is not in use. It is often 
made in the form of a bottle with 
a cork through which passes a rod 
attached to the zinc, which provides 
for the lifting of the zinc clear of the 
liquid when the cell is not being 
used. 

By the chemical action of the elec- 
trolyte on the plates when the circuit 
is closed, a strong electric current is 
excited, positively charged ions of 
hydrogen and metallic radicle pass 
from the zinc to the carbon element, 

at the same time negatively charged ions of oxygen and 
acid radicle pass from the carbon to the zinc. 

The E. M. F. of the cell is about 2 volts. It is used when 
a strong current is required for cautery or small incan- 
descent lamp or working an induction coil. With a few of 
these cells collected in parallel a very strong current is pro- 
duced for a short time but polarization takes place rapidly 
within the cells and internal resistance causes a rapid fall in 
the current. It is a useful form of cell, being always ready 
for use and producing a strong current. Until recently 
small batteries made of this type of cell were much used 
for producing high current strength for cautery and it was 
probably the most important of the single fluid cells, but the 
advent of the accumulator and switchboard has detracted 
from this importance. 

Persulphate of Mercury Cell. — This is another type of 
single fluid cell from which a high E. M. F. is obtained. 

It is constructed of a zinc plate for the positive element, 



Fig. 9. — Bichromate of 
potash cell. 



58 CELLS 

carbon for the negative element, and persulphate of mer- 
cury in solution for the electrolyte — the depolarizer is 
persulphate of mercury. By chemical action, when the 
circuit is closed, hydrogen electro-positive ions appear at 
the carbon where they unload their electrical charges to that 
element and H unites with the persulphate of mercury in 
the electrolyte solution to form sulphuric acid and deposit 
metallic mercury. 

The sulphuric acid thus formed acts on the zinc element. 
The chemical affinity of the hydrogen for the persulphate 
of mercury by which the gas bubbles .are removed from the 
surface of the carbon constitutes the depolarizer. 

The E. M. F. is 1.5 volts and the internal resistance is 
low. It is a much-used cell for medical purposes. Many 
improved forms have been invented in which the mercury 
in the electrolyte has been utilized to amalgamate the zinc 
and by improvements in the depolarization of the cell a 
constant and lasting cell has been made. 

The cells described so far are all single fluid cells, there 
now remain to be described briefly one or two forms of 
double fluid cells; that is, cells in which each element is 
surrounded by a different fluid, one of which is the electro- 
lyte and the other the depolarizer. Of these the Bunsen, 
the Grove, and the Daniell are the best known. 

The Bunsen Cell. — This consists of a glass cell containing 
a zinc plate which forms the positive element, a porous pot 
containing a stick of carbon and a strong solution of nitric 
acid forms the negative element, the electrolyte is a dilute 
solution of sulphuric acid which is placed in the cell about 
the zinc and porous pot. The nitric acid is the depolarizer. 
By the chemical action of the cell zinc is acted upon by the 
sulphuric acid to form zinc sulphurite and liberate hydrogen 
ions which migrate to the negative element conveying posi- 
tive charges of current, here the current is conducted away 
by the carbon, and hydrogen gas collects on the porous 
pot, the depolarizer (nitric acid) combines with the free 
hydrogen to form nitric-peroxide and water, and depolarizes 
the cell by dispersing the gas bubbles. 



THE DANIELL CELL 



59 



The current strength from this cell is greater than any 
of the single fluid cells, because of the small resistance 
within the cell by the perfect depolarization; the E. M. F. 
is about 2 volts, and internal resistance only a fraction of 
an ohm, and maximum current strength about 10 amperes. 

The strong acid electrolyte of this cell soon destroys the 
zinc element, so that this cell is not a lasting one. The 
poisonous fumes of nitrogen peroxide, which are given off in 
the process of oxidization is a great objection to this form 
of cell; it should not be kept in a room with instruments. 




Fig. 10.— Bunsen cell. 



It produces current for cautery loop or lamp and a battery 
of these cells can be used to charge accumulators where 
current from the main is not available. 

The Grove Cell. — This cell has the same construction as 
the Bunsen which is a modification of it. The negative 
plate in the porous pot is platinum, but owing to the cost 
of this metal, carbon is substituted in the Bunsen cell, 
otherwise the fluids and their chemical action in the cell are 
precisely the same. 

The Daniell Cell. — This cell is constructed with different 
variations of the following principle: The positive element 



60 



CELLS 



gen in passinj 



is a rod of zinc which is placed in the centre of a porous 
pot in the centre of the cell, the zinc is immersed in the 
electrolyte which is a dilute solution of sulphuric acid or 
zinc sulphate. The negative element is copper which forms 
the inner lining of the cell, the space between it and the 
porous pot contains a saturated solution of sulphate of 
copper, with usually some crystals of sulphate of copper 
to add to the supply of the salt in solution. The second 
fluid is the depolarizer of the cell. 

By the chemical action of the H 2 S0 4 on the zinc, zinc 
sulphate (ZnS0 4 ) and hydrogen (H 2 ) are formed; the hydro- 
from the porous pot combines with the 
copper sulphate (CuSo 4 ) to form sul- 
I phuric acid (H 2 S0 4 ) and copper (Cu). 
The H 2 S0 4 formed replenishes the sup- 
ply of electrolyte. The copper ions 
unload their charge of current to the 
copper element and deposit copper on 
the lining of the cell. There is no polari- 
zation of the cell, as the hydrogen is used 
up in chemical combination with the cop- 
per sulphate and the copper deposited 
on the negative element merely thickens 
the copper lining of the cell. 

By the perpetual change of ions in this 
form of cell it remains active for a long 
time; the positive element (zinc) becomes 
destroyed in time but is readily replaced 
and the cell is then as good as new. The negative element 
(copper) will always remain active because it is being added 
to when the cell is working. The electrolyte is also replen- 
ished by the formation of H 2 S0 4 at the porous pot. 

The E. M. F. of the Daniell cell is a little over one volt 
and was originally taken as the standard unit of electro- 
motive force, being sufficiently near the volt and being 
nearly constant. 

The internal resistance is practically nil, but placed at 




Fig. 11. —Daniell cell. 



SECONDARY BATTERIES OR ACCUMULATORS 61 

an estimate of 0.15 ohm the current strength from one of 
these cells would be : 



1 volt c r 

6.6 amperes. 



0.15 ohm 



Three of these cells connected in parallel will produce 
nearly 20 amperes current strength. 

The disadvantage of all acid fluid cells is that the perish- 
able element should be withdrawn from contact with the 
electrolyte when the current is not required ; this leaves the 
cells open to evaporation of their fluid contents, and also 
the liquid is easily spilled. They are not as clean as the 
Leclanche cells and require replenishing frequently. The 
refilling, however, is not a difficult matter. In places where 
electrical supplies are not easily obtained the Daniell cell 
battery might be useful to those who have only occasional 
use for cautery and light, but their use has been almost 
completely superseded by the dynamos and secondary 
batteries (accumulators) . 

Secondary Batteries or Accumulators. — This type of battery 
is so constructed that when it runs down it can be again 
charged by passing a current through it. It is made, in 
one type, of thin plates of lead molded in the form of a 
grid, that is, holes punctured in the surface of the plates; 
these plates are placed close together but carefully sepa- 
rated by some insulator interposed at the top and bottom 
of the cell so that they are in no electrical contact except 
through the electrolyte, which consists of a solution of 
sulphuric acid (about 1 part to 5 of water). The plates 
which form the positive pole are pasted with red lead, that 
is, the holes of the grid are filled with the red lead; and the 
plates which form the negative pole are filled with sponge 
lead; all the plates of the positi\ T e sign are connected outside 
the cell by metal, bringing them to one terminal, and all 
the plates of negative sign are similarly connected, there 
being always one more negative than positive plate, and 
are alternately placed, a positive and a negative. 



62 CELLS 

There are many variations in the method of construction 
of accumulators which it is unnecessary to enumerate or 
describe. This one gives the principle of the "storage 
battery" as it is sometimes called. The arrangement 
and number of plates is carried out with the intention of 
increasing the current with the least amount of potential, 
i. e., it diminishes the internal resistance. 

Four or six cells connected in series form a battery, each 
cell of which has a potential of 2 volts, making a total 
E. M. F. of 8 or 12 volts, according to the respective number 
of cells. The capacity of the cells varies according to the 
size of the plates, and the discharge of current is recorded in 
ampere-hours, i. e., current can be maintained at a certain 
number of amperes for so many hours, e. g., six cells with a 
capacity of say 24 amperes when charged may be discharged 
either at the rate of 1 ampere for 24 ampere-hours or 2 
amperes for 12 ampere-hours or J ampere for 48 ampere-hours. 
When the accumulator is run down, which can be determined 
by an amperemeter (usually called ammeter) in circuit, it 
can be recharged from the opposite direction to that in which 
it discharges. This is done by attaching the positive pole of 
the source of current for recharging to the positive pole of the 
battery and the negative to the negative of the battery. The 
recharging of an accumulator battery may be accomplished 
with current from a number of Daniell or Bunsen cells 
connected in series, having an E. M. F. of at least 10 per 
cent, higher than that of the battery to be charged, and 
the current must be allowed to pass for about 25 per cent, 
longer than the capacity of the cells, i. e., a cell of 4 ampere- 
hours' capacity will discharge for 8 hours at J ampere, but 
must be charged for 10 hours at \ ampere. 

If continuous main current for lighting purposes is avail- 
able it is far easier and cheaper to recharge accumulators 
from this source, provided the voltage of the main approxi- 
mates to that of the accumulators or that suitable means 
be taken to reduce it. 

In recharging accumulators the capacity of the cells 
should be taken into account and the charging current 



SECONDARY BATTERIES OR ACCUMULATORS 63 

measured with an amperemeter and calculated in ampere- 
hours to correspond with the capacity of the cells; the 
rate of charging should not be too rapid; the most efficient 
rate being usually marked by the makers, and is usually 
about one-tenth the capacity. Those accustomed to the 
recharging of accumulators can determine when fully 
charged by the sound of effervescence of gases in the elec- 
trolyte of the cells, when they are only partly charged slight 
effervescence is audible, and when fully charged a distinct 
noise of active effervescence is heard within the cells. 




Fig. 12. — Resistance lamps. 



In charging from the main, the correct poles of both 
source of current and battery must be determined, this 
can be carried out by methods already described (p. 42). 
The like poles of both are connected and a resistance, the 
amount of which is determined by the current required, 
is placed in circuit between the negative pole of the battery 
and negative of the current supply. The current is passed 
from the positive pole of the main to the positive terminal 



64 CELLS 

of the accumulators, through the plates and electrolyte 
within the cells and out at the negative terminal, and 
through the resistance; carbon-filament lamps of different 
powers are often used as a cheap and convenient form of 
resistance, several usually being employed in parallel. 

The accumulator is useful for heating a cautery loop 
and for lighting mouth lamps. It has a very useful place 
in the surgery, especially where the current is not available 
from a dynamo source. The battery is always ready for 
immediate use as long as it is charged: when run down it 
is easily recharged by sending it to the power house of a 
dynamo machine or to the makers, and it lasts for a number 
of years if properly cared for, the acid kept at the right 
strength, and if not allowed to run down completely before 
it is again charged or if not badly charged, that is, charged 
too quickly with too strong a current. 

The modern form of switch-board which is made for use 
where dynamo current is available has quite superseded 
the secondary battery. It is certainly far more convenient 
for many purposes, which, until its introduction, the storage 
battery was the only available means of procuring current 
in that form — but the accumulator will always find a use- 
ful place in the surgery of dentists situated in places where 
the street current is not available or not installed, or where 
it is alternating and the current required is a continuous 
current, or where a portable battery is required. 

The ordinary dental motor engine can be run by a col- 
lection of accumulator cells arranged in series, 6 cells will 
produce an E. M. F. of 12 volts, which is ample to run the 
dental engine indefinitely by keeping the cells charged. 

The Edison Storage Battery. — This form of accumulator 
is one of the latest inventions of Mr. Thomas A. Edison, 
which bids fair to revolutionize the storing of electric current 
for many purposes, certainly for dental purposes there is no 
method more suitable. It does away with the lead and 
acid so objectionable in the lead plate form of storage cells, 
eliminates the element of care and knowledge necessary in 
the working of the lead cells, while the life of the cells is 



THE EDISON STORAGE BATTERY 



65 



increased many fold; reduced size and weight with the same 
storage capacity are improvements of great value. The 
cells are made in various sizes and numbered by the makers 
according to their capacity, the ampere-hour output depend- 
ing on the number and size of the plates, but the voltage 
is the same, viz., 1.2 volts per cell. The voltage, it will be 



/~~\ 



Fig. 




Positive and negative plates, A.4 type. 



observed, is less than that of the lead cells. Each cell of A.4 
type (which is the size which would make a useful battery 
for working a dental engine) contains four positive and five 
negative plates. " The negative plate is comprised of twenty- 
four rectangular pockets supported in three horizontal rows 
in a nickel-plated grid, each pocket being \ inch wide and 3 



inches long. 
5 



The pockets are made of thin nickel-plated 



CELLS 



steel, perforated with fine holes. Each pocket, after being 
filled with iron oxide, is subjected to high pressure, so that 
it becomes practically integral with the supporting grid. 

"The positive plate consists of two 
rows of round rods or pencils, 30 in 
number, held in vertical position by 
a steel supporting frame. The per- 
forated tubes into which the nickel 
active material is loaded are made of 
nickel-plated steel. These tubes are 
put together with eight steel rings." 
The plates consist of iron oxide for 
the negative and nickel hydrate for 
the positive plate acted on by a solu- 
tion of caustic potash in pure water, 
which is the electrolyte. The cells 
are assembled in the usual manner, a 
positive and a negative plate alter- 
nately, there being always one more 
negative plate than positive. The 
plates of each sign are connected to 
a nickel-steel rod and kept the proper 
distance apart by washers and nuts 
which hold them firmly in position. 
Altogether the cells when complete 
are of most substantial mechanism 
with nothing to go wrong with 
of plates, no fear of short-circuiting 
the battery may be short-circuited 
and discharged at once without injury to the plates. The 
battery is kept in order by simply replenishing with pure 
water when necessary, and charging and discharging may 
be done almost indefinitely without fear of the plates being 
used up, as in the case with the ordinary lead-plate cells. 

The cells to form a battery are connected in series, five 
cells of the type described will work a dental engine of G 
volts winding for a very long time, revolving at a speed of 
from 1000 to 3000 revolutions per minute. There are no 




Fig. 14. — Assembled posi- 
tive and negative plates. 

them, no buckling 
doing damage, for 



ARRANGEMENT OF CELLS 



67 



fumes from the electrolyte, so that the battery may be 
placed in a neat hardwood case and kept in the surgery in 
close promixity to the engine. 

Arrangement of Cells.— The E. M. F. of cells has been 
shown to depend on the dissimilarity of the plates, the 
conductivity of the electrolyte, the area and proximity of 
the plates and the internal resistance set up by polarization 
within the cell; the size of the cell has no effect on the E. M. F. 
of the cell, a small Leclanche cell will have almost the same 
potential as a large one ; with the increase of size (so long as 
the plates are of the same nature) the internal resistance 
(r) is increased, so that the output of current strength is 
about the same. 



Fig. 15. — Cells in series. 



Cells in Series. — The E. M. F. of one Leclanche cell 
is about 1.47 volts, which when resistance is taken into 
account produces a current strength quite inadequate for 
therapeutic purposes, but this form of cell has been shown to 
be one of the most useful for producing current for dental 
ionic-medication; in order, therefore, to increase the current 
strength a number of cells are connected in series, that is, 
the zinc of the first cell is connected with the carbon of 
the second and so on till all are connected, that will leave 
the terminal carbon at one end free and the last zinc at 
the other end free. 

The potential of the cell is from the zinc to the carbon 
within the cell, therefore at the terminal the flow of current 
is + at the carbon and — at the zinc. 

According to Ohm's law, if each of these cells has an 



68 CELLS 

E. M. F. of 1.47 volts, by collecting 6 of them in series 
the E. M. F. is increased to nearly 9 volts. 

1.47 volts X 6 = 8.82 volts 

and three times that number of cells connected in the same 
way will give about 

1.47 volts X 6 X 3 - 26.42 volts. 

The voltage of a cell or collection of cells is simply the 
electro-motive force. What most concerns us is the current 
strength which these cells will produce, and to find this 
the internal resistance of the cells and external resistance 
of the circuit must be calculated. The resistance of a 
Leclanche cell varies. When the circuit is first closed it is 
stronger than after it has been closed for some time because, 
as we have seen, polarization takes place faster than de- 
polarization, but say it is on an average 2 ohms and the 
external resistance of the circuit 1 ohm, the current strength 
(c) of one Leclanche cell would be worked out by Ohm's 
law. 

~ 1.47 volts 1.47 „ An v inn 

C = = = 0.49 ampere = 490 ma. 

Rl + r2 3 

Now if we take 18 cells in series and consider the resistance 
(R) and internal resistance (r) we shall find that the resist- 
ance has a very marked effect on the current strength, for 
instead of the current strength being 18 times as great it 
is only raised not quite twice as much, thus 

~ 1.47 volts X 18 cells 26.42 volts n _-„ --. 

C = — = = 0.714 amp. = /14 ma. 

Rl + (r2 X 18) 1 + 36 ohms 

It may be taken that this output of 714 ma. current 
strength is fairly accurate so far as 18 Leclanche cells are 
concerned; this is about the number of these cells which 
will constitute a useful battery for ionic medication for 



ARRANGEMENT OF CELLS 69 

all dental purposes, the full current obtainable from such 
a battery will of course be more powerful than it is possible 
to use in the mouth of a patient, but the current weakens 
after the battery has been in use for a time and it is best 
to have a reserve of current strength; it is essential to have 
it controlled by a finely graded rheostat in circuit, through 
which the current must pass before reaching the patient. 
The resistance of the body must now be taken into con- 
sideration. If a milliamperemeter be connected in circuit 
with the current flowing from the terminal of the battery, 
when the circuit is closed without the resistance of the 
body in circuit but with nearly all the resistance of the 
rheostat in use, the milliamperemeter needle will be violently 
deflected 5 or 10 milliamperes, the resistance of the wire 
leads being only one or two ohms; but a very different 
result will be observed if the resistance of a patient be 
placed in the circuit. Take for instance a patient having 
a resistance of 2000 ohms, a considerable amount of current 
will be required from the battery to register two or three 
ma. on the milliamperemeter dial. According to Ohm's 

„ 1.47 volts X 18 cells 26.42 volts - ~ 10 

C = = = 0.012 amp. = 12 ma. 

R2000 + (r2 X 18) 2000 + 36 ohms 

law 12 ma. will then be the greatest amount of current 
strength which will be available from a battery of 18 cells 
with the resistance of a patient of 2000 ohms in series. This, 
as has been said, must be controlled by a rheostat which 
is really resistance placed between the battery and the 
patient to regulate the output of current strength, so that 
instead of the full 12 ma. passing, only 1 or 2 ma. pass 
according to the requirements. 

To summarize, it has been shown that 18 Lechanche cells 
connected in series produce an electro-motive force of about 
26 volts and a maximum current strength of about 714 ma. 
That with the resistance of the body of 2000 ohms in series 
the maximimi current strength is about 12 ma. That the 
maximum current strength of one cell is about 490 ma., 



70 



CELLS 



which is only slightly increased to 714 ma. by connecting 
18 cells in series, showing that the E. M. F. is added together 
while their remains almost the same. The current which one 
cell will force through a large resistance will be much less than 
the amount which 18 cells will force through a similar resist- 
ance, although without any external resistance the C is about 
the same, hence the necessity for a number of cells in a battery 
which is intended for use with the body as resistance; the 
pressure, potential or E. M. F. must be of proportions great 
enough to overcome the resistance met in circuit. 




Fig. 16. — Cells in parallel. 

Cells in Parallel. — To connect cells in parallel all the 
terminals of one sign are connected together with one wire 
to form one pole of the battery and all the other terminals 
are connected to form the other pole; by this arrangement 
the collection of cells act like one cell, the internal resist- 
ance, however, is considerably reduced, so that a greater 
maximum current is obtainable. This arrangement is 
therefore only of use when the resistance of the external 
circuit is very low (and its chief use in medical and dental 
work is for heating cauteries where low E. M. F. and a 
high current is required). 

Cells are connected in parallel when a large current 
strength is required such as for cautery. To get the greatest 
amount of current strength the choice of cells should be 
those with the least internal resistance, so that for this 
purpose Leclanche cells are least serviceable. The bichro- 
mate cells and Grove's cells are useful because the E. M. F. 
of these cells is greater, owing to the nature of the electro- 



ARRANGEMENT OF CELLS 71 

lyte, the proximity of the plates, and the area of the plates. 
The E. M. F. of a bichromate cell is about 2 volts with an 
internal resistance of about 1 ohm, one of these cells will 
produce considerable current strength for cautery or light, 
but if six are arranged in parallel the current strength is 
materially increased. If we add two ohms for the external 
resistance of the cautery wires, according to Ohm's law the 
current strength can be calculated: 



r, 2 volts X 6 cells 12 _ _ x 

C = — = — = o.o amperes. 

R2 + rf 2} 

If one such cell be tried we should have a current by the 
same calculation: 

2 volts _ 2 n „ 

= 0.6 ampere 



R2 + 1 ohm 



which would be insufficient to heat a cautery loop or light 
a small lamp. 

Thus it is seen that by adding cells in parallel the E. M. F. 
remains practically the same as one cell but the current 
strength is greatly increased. 

Accumulators for cautery work are better than voltaic 
cells, their internal resistance being very low. 

Cells in Multiple Arc. — This is another method of 
connecting cells which has the effect of reducing the internal 
resistance and increasing the current strength. One way 
of arranging cells by this method is as follows : take six cells 
and connect three together in series, and the other three also 
in series, then join the positive pole of each collection of three 
to form one pole, and the negative pole of each to form the 
other pole; the effect of this compound connection will be to 
double the size of the cells and to halve their number. This 
can be shown by calculating as before (take for example the 
bichromate cell with E. M. F. of 2 volts and internal resist- 
ance of 1 ohm and say the external resistance is 0.5 ohm). 
The E. M. F. would be that of three cells (3X2 = 6 volts) ; 



72 CELLS 

the internal resistance would be that of three cells of double 
the size (1 ohm X 3 t 2 = 1.5); therefore 

n E v 6 6X2 12 ' . 

O = X - = — - = — =1.3 amperes. 

R+r R + r X 6 1+0.5X6 9 

Another variation of the compound connection of cells 
consists in collecting each group, say 3 cells in parallel and 
then these two groups in series. This will also reduce the 
internal resistance and therefore produce a greater current 
strength. 

The arrangement of galvanic cells in series and in parallel 
have a useful place in electro-therapeutics, especially where 
it is necessary to take about instruments to work away 
from the surgery or where an alternating current circuit is 
supplied by the mains; but in dental practice where nearly 
all work is done in the surgery, batteries are nearly entirely 
superseded by the use of current from the main, where 
this is continuous, which can be controlled and regulated 
by switchboards from which the current can be obtained 
in every conceivable form for every requirement. Alter- 
nating current mains can be used but they necessitate a 
motor-dynamo to convert the current into continuous. 

The battery of cells in series, however, is preferred by 
many who use a continuous current for ionization, and the 
advantage undoubtedly is that it is impossible to obtain a 
severe shock from it. 

Density.— We have seen that the distribution of the 
current on a charged conductor is on its surface, and that 
if the surface is spherical the distribution is all over that 
surface evenly, but if it be pointed the density is greatest 
at the point. So, too, if it be knife-edged the edges will 
display greater density, whereas the flat surfaces are less 
charged. These facts have an important bearing on the prac- 
tical use of the current. In the construction of electrodes, 
the purpose for which they are required and the manner 
in which they are to be applied are considerations which 
should be carefully thought out with regard to the density 



ARRANGEMENT OF CELLS 73 

of the current likely to be produced by the shape, size, 
and diameter of the conductor. If it is required to pass a 
current of 25 ma. into the body, a flat electrode of 5 cm. 
diameter would be twice as painful to the patient as one 
10 cm. in diameter, because the density in 5 cm. area would 
be so much greater. So, too, a fine-pointed conductor will 
intensify the current at the point, which will be painful even 
with a current strength of 2 ma., whereas a conductor which 
is round and 5 mm. in diameter would not be felt at all with 
the same current strength. Also a flat, knife-like conductor 
will intensify the current at the edges while the flat surfaces 
will have a less density, but if the cross-section be increased 
and the edges rounded the density will be diminished, being 
more evenly distributed over the whole surface. 

Taking these points into consideration it becomes pos- 
sible to use more current, say, for instance, in a pyorrhea 
pocket without discomfort to the patient, or on the other 
hand, to produce perfect sterilization in the root of a dead 
tooth by introducing a very fine-pointed conductor, a dead 
tooth having little sensation except the conductor reaches 
the apex. Density then has to be considered for the comfort 
of the patient in the efficient use of the current especially 
in mucous or periodontal membrane; one of the important 
factors in ionic medication is : the greater the current strength 
that is possible to be used without pain, the more penetrating 
will the medication be, and in order to obtain this it is neces- 
sary carefully to consider the area and shape of the electrode 
which is to convey the current to the parts. It is often 
difficult to use an electrode large enough to diminish the 
density sufficiently to cause no discomfort when 4 or 5 ma. 
is the current strength for ionization of affections about the 
roots of live teeth or the gingival margin. 



CHAPTER IV. 

MAGNETIC FIELD, DYNAMO CURRENTS AND 
BATTERIES. 

Induced Currents — Self-induction — Induction Coil — Secondary Coil — 
Continuous Current — Alternating Current — Transformers — Batteries — 
Home-made Battery — Cautery Battery — Accumulator Battery. 

When a magnet is brought in close proximity to iron 
filings it attracts the filings and they cling to its surface. 
If the filings are placed on paper and the magnet placed 
under the paper and the paper slightly tapped the filings 
will be observed to arrange themselves in definite lines and 
curves. This indicates that for some distance around the 
magnetized iron there is a space or field which is permeated 
with the influence or force of the magnetism; this field is 
termed the magnetic field. It exists about all magnets, 
and experiments have been made to prove that the force 
created in this field takes certain lines and curves. In a 
bar magnet for instance, the one end is north pole and the 
other south pole; if it is balanced on a pivot in the centre, 
which is the equator or neutral zone of the magnet, the north 
pole will swing to the north as any ordinary pocket compass 
does. From the ends of the magnet the magnetic force 
radiates in curves in the direction from one pole to the other, 
there being a considerable space about the magnet which is 
the magnetic field. The strength of the force in a bar 
magnet is greater at each end. In a curved magnet, on the 
other hand, the greatest force is exerted between the two 
poles from their nearest point. 

This magnetic force which permeates the field about 
the magnet is conducted by the air, but air has been found 



MAGNETIC FIELD 



75 



to be a poor conductor of magnetism, whereas iron is a good 
conductor and if the magnet is strong enough iron brought 



in contact 
degree. 



with it will itself 



become magnetized to 



some 







X ; < :: ::^ ; >x\ 


\\ \ \ 


i ' ' / 


~----~i 


N < 


Magnetic axis 




l-'-'- > ' 


.-■':'-';. 


n < m o 





Fig. 17. — Lines of force of magnetic field. 

A temporary magnet is made by winding insulated copper 
wire around an ordinary piece of soft iron bent in the 
shape of a horseshoe and by passing an electric current 
through the wire. As the wire does not touch the iron it is 
evident that the magnetism which is imparted to the iron is 




Electro-magnet. 



obtained from a magnetic field about the current-conducting 
wire. This magnetic field exists around all wires conducting 
electric current and the force of the field is intensified by the 
curving of a wire (making a spiral of it, as by winding stiff 



76 MAGNETIC FIELD, CURRENTS AND BATTERIES 

copper wire around a lead-pencil and removing the pencil), 
and also by the intensity of the current passed through the 
wire; the field is also stronger when the iron is placed in it. 

A magnet made by passing current through wire encircling 
a piece of soft iron is only magnetic so long as the current 
is passing, it is a temporary magnet. 

Sir Oliver Lodge points out that the magnetic field about 
a current-conducting wire exerts force in the field exactly 
similar to force about a magnet, and he describes it as elec- 
tricity in rotations; many experiments have been performed 
with the ordinary compass-like magnet in a magnetic field 
to show the rotatory action of the current in a magnetic 
field. If a magnetic compass be suspended in the air it will 
point north and south, but if a wire conveying current from 
any electrical source be brought parallel above the compass 
so that it also runs north and south with the positive and 
negative running from the south to the north, when the wire 
approaches the compass near enough to bring it into the 
magnetic field, the N-point of the compass will deflect to 
the west, showing that the force of the field is outward and 
backward, rotatory, in the same direction as the lines 
described about an ordinary magnet. On this principle of 
the force of the magnetic field, galvanometers are constructed 
to measure the force of current strength. 

The energy derived from the field of force about an 
insulated conductor of current by which temporary magnets 
are created is termed electro-magnet, and as the magnetism 
so derived ceases as soon as the current ceases, the principle 
is applied in the construction of many electrical appliances 
in which rise and sudden fall of energy operates in mechanical 
devices. 

An electro-magnet has been devised for use with the 
ordinary street current with a lamp in circuit as a reducer 
of the current, which when applied to the cavity of a tooth 
or near the orifice of a root canal, in which is a broken drill 
or any piece of steel, if the metal is loose, will extract it with 
ease by the powerful electro-magnetic force. Magnetic 
force is not conducted in the same way that current is, so that 



INDUCED CURRENTS 77 

the energy is not felt by a patient. Electro-magnets have 
been constructed of enormous power, capable of raising tons 
of metal. The strength of electro-magnetic field depends on 
the current strength which is used in creating it. 

Induced Currents. — From the foregoing it has been shown 
that there is a field of magnetic force about a wire con- 
ducting current. Faraday discovered that if another wire 
was brought within the influence of this field, it had the 
power of inducing current at the moment of turning on 
and turning off the current (that is, at the make and break 
of circuit) ; also if the current strength be varied or changed 
in direction. The current so produced in the adjoining 
wire is momentary and occurs at the make or break or 
change of potential. Also, the direction of the induced 
current varies with the make and break of the circuit in 
the primary or current-conducting wire; when the current 
is turned on in the first wire the momentary induced cur- 
rent in the second wire flows in the opposite direction, and 
when the current is turned off the current is again induced 
in the second but in the same direction as the primary 
wire. The same phenomenon of induction takes place 
when the current is increased in the primary wire, the 
induced current flows in the secondary wire in the opposite 
direction, but when it is reduced in strength the induced 
current flows in the same direction as the primary wire. 
This induction of current in a magnetic field about a wire 
conducting current is due to the expansion and contraction 
of the magnetic field of force. The above is the simplest 
form of induction that can be imagined and may be prac- 
tically illustrated in the adjoining sketches of two parallel 
wires, the one conveying current and the other inducting 
current, the arrows showing the direction of the induced 
current at the moment of make or break of circuit. 

While the current is flowing uniformly in the primary 
circuit no induced current is formed ; it is only at the instant 
of make and break or increase and decrease of potential that 
induction takes place. 

The magnetic force in the field about an electric wire 



78 MAGNETIC FIELD, CURRENTS AND BATTERIES 

is in the direction at right angles to the direction of flow 
of current in the wire, precisely in the same manner as the 




Fig. 19. — A, primary current at make; B, induced current at make. 

field about a magnet, forming, as it were, concentric circles 
about the wire; when the wire is bent in the shape of a 
coil the magnetic field of force is increased, but the resistance 




Fig. 20. — A, direction of current before break; B, induced current at break. 



is also increased, so the strength of the magnetic field will 
depend on the strength of the current and will be proportional 






INDUCED CURRENTS 



79 



to the current and the field of force. The introduction of an 
iron core will also, as has been shown, increase the strength 
of the field. 




Fig. 21. — Field of force about a wire. 



If a secondary coil be introduced into the magnetic 
field of a stationary primary coil and be moved away or 
toward it, current is exerted in the secondary coil; this 
effect is produced by the magnetic circles of force about 




Fig. 22. — -Field of force in a coil. 



the active coil being cut into by the circles of force in the 
induced current of the other coil. This principle of in- 
duction is carried out in the production of current by 



80 MAGNETIC FIELD, CURRENTS AND BATTERIES 

dynamos in which armatures are constructed to cut the 
lines of force from the field magnets by their motion. 

Self-induction. — This takes place in a simple coil or 
primary wire and is the effect of passing a current through 
a coil by which a magnetic field is set up about the con- 
ducting wire of the coil and a reaction of E. M. F. is set 
up in the conducting wire itself at the make and break of 
the circuit; at the make of the circuit the current is resisted 
by the induced current in the magnetic field in an opposite 
direction, and at break of the circuit the induced current 
is momentarily conducted by the conducting coil in the 
same direction as the current in circuit. In other words, 
each coil induces a current in the next. If a current from 
a battery be passed through a single coil and the terminals 
be so arranged that there will be a small gap over which 
a spark can pass, on breaking the circuit a spark will be 
observed at the spark gap of a size large enough to ignite 
an ordinary gas jet. The current which produces this spark 
is the self-induced current in the coil. If the wires from 
the same battery do not include a coil in circuit, the breaking 
of the current with a similar spark gap will produce no visible 
spark. The strength of the self-induced current is greatly 
magnified when the magnetic field about the coil is increased, 
as when the current is supplied from an alternating dynamo 
and still further increased when an iron core be introduced 
into the centre of the coil on the principle of an induction coil. 
The extra resistance introduced into the coil by the strong 
magnetic field produced by the alternating current on the 
magnetism about the iron core, reinforces the self-induced 
current and on breaking the current a large spark is produced 
according to the strength of the current employed; more- 
over, the strength of the self-induced current will be increased 
or diminished by the number of turns in the coil, the larger 
the number of turns in the coil the greater will be the magnetic 
field, and the stronger the self-induced current. 

The resistance set up in such a coil by the self-induction 
current is very much greater than the ordinary resistance 
of the same wire not formed in a Solenoid, as the hollow 



THE INDUCTION COIL 81 

spiral of a self-induction coil is termed; the resistance 
only occurs when the current begins to flow or increases 
its strength, a steady current meets with no resistance from 
self-induction. 

The Induction Coil. — This is probably one of the commonest 
and best-known electrical devices in use for medical pur- 
poses. So far it has been little used in dental treatment 
and it is hard to conceive many uses to which it can be 
directly applied. The principle of the induction coil should, 
however, be studied, for it enters into the construction of 
numerous electrical devices, which are of importance to 
dental science and has a direct bearing on them, such as 
the .r-ray and high-frequency coils. It consists of a primary 
coil, a secondary coil, an interrupter, with sometimes a 
condensor. 

A simple form of coil consists of a core of iron or bundles 
of iron wire around which is wound the primary coil con- 
sisting of a number of turns of wire which is insulated 
with silk wound around it. The core must be carefully 
insulated from the primary coil. The coil is connected 
with a battery and conveys the primary current. The 
interrupter is placed opposite the core and is a vibrating 
spring with a metallic head which affords the spring mo- 
mentum when set in motion. A stationary adjustable 
screw with a platinum point is fixed at the middle of the 
spring. The spring and primary coil are connected to one 
pole of the battery and the adjustable screw is connected 
to the other pole. When the current is passed through the 
coil the magnetic field which is set up about the coil con- 
verts the iron core into an electro-magnet which attracts 
the metal head of the spring and breaks the contact at the 
adjustable screw; contact being broken, the current at that 
instant ceases to flow in the coil and the core loses its 
magnetism, therefore the metal head of the spring swings 
away from the core, and in doing so by its own momentum 
once more establishes contact by touching the metal point 
of the screw. This process repeats itself in rapid succession, 
making and breaking the contact and in this way induced 
6 



82 MAGNETIC FIELD, CURRENTS AND BATTERIES 

currents are established and increased in the magnetic field 
about the primary coil which also intensifies the electro- 
magnetic force of the core. This simple form of induction 
coil does not admit of any regulating of vibratory current 
set up by make and break, and the force of the induced 
current established in the magnetic field about the core will 
depend on the strength of the battery which is producing 
the primary current. The current from two Leclanche 
cells in such a coil will often induce a maximum vibratory 
current greater than one can bear when the terminals are 
held in the hands. The maximum E. M. F. produced in 
both coils is higher than the battery supplying the energy 
to the apparatus. 



Interrupter 




Adjustable Screw 

Fig. 23. — Induction coil. 



There are many devices in the arrangement of the coil 
and the core by which the current strength can be regulated. 
This is done by introducing resistance into the circuit to 
control the current strength in such manner that it can be 
varied, or by resistance introduced into the primary coil 
which can be adjusted to vary the induced current. This 
latter is usually done by having a movable adjustable core 
or a movable secondary coil, or a brass tube to slide over 
the core, or a combination of these may be used. 

A simple form of induction coil in which the current 
strength can be regulated consists of a primary coil as 
already described, but a stationary magnet is introduced 
instead of the core. The current from a battery passes to 



SECONDARY COIL 83 

a stationary upright to which is attached a spring which 
is in contact with an adjustable screw, from the screw it 
passes to the primary coil which is wound on a bobbin, 
the return wire is wound around a stationary core fixed 
under the spring and from this it is taken to the other pole 
of the battery; this second core then serves to interrupt 
the current in the same way as described aboA T e. 

Secondary Coil.- — A secondary coil is wound with a great 
number of turns of insulated wire, and slides over the main 
primary coil so that it is in the magnetic field and can be 
passed completely over the primary coil or drawn away 
to cover only a very small part of the end of it. When 
the circuit is closed the current acts on the coil as already 
described and the strength is varied by moving the sliding 
secondary coil. The secondary coil becomes charged with 
induced current which on make is in the same direction 
and on break is in the opposite direction to the flow of 
the primary current; by sliding the secondary coil over the 
primary, or pulling it away, the induced current is varied 
and the strength of the vibratory current from the coil is 
increased or decreased by the regulation of the intensity of 
the magnetic field and induced current set up about the coil. 

The arrangements of the wires of an induction coil are 
best understood by diagram; by following out the lettering 
of the figures which is the same in both diagrams, the course 
of the current and its action on the secondary coil and the 
magnet are easily comprehended. The diagrams are from 
Lewis Jones' book. "One pole of the battery is connected 
to the coil at A. The current then passes by the adjusting 
screw B, the vibrator H, and the support K, to the magnet 
D, which actuates the contact-breaker. After traversing 
this the circuit gives off a branch to the binding screw P, 
and is continued to the primary coil EE, the return wire 
from which again gives off a branch to the secondary binding 
screw at P, and is then continued to the other pole of the 
battery. The two binding- screws at P are thus in connection 
with the two ends of the primary coil, and by means of 
electrodes attached to them the patient may be treated with 



84 MAGNETIC FIELD, CURRENTS AND BATTERIES 

the primary current of this coil. The secondary coil F is 
wound on a separate hollow bobbin and has its terminals at S. 
This bobbin is made to slide like a sledge on guides, so that 




Fig. 24. — Arrangement of wires of an induction coil. 

it can be made to approach or recede from the primary coil. 
At G a handle is seen attached to the iron core which can 
slide in and out of the primary coil and so further modify the 
electro-motive force induced in the primary and secondary 
coils by varying the strength of their magnetic field." 




Fig. 25. — Induction coil. 

It can be readily seen from these diagrams that when 
the circuit is closed the current passes through the coil 
and returns by way of the magnet and renders it electro- 



DYNAMO CURRENTS 85 

magnetic, and it then attracts the vibrator which causes 
the break in the current, the magnet at that instant loses 
its electro-magnetic force and releases the vibrator which 
springs back into contact with the adjusting screw, and 
once more closes the circuit. This is repeated in rapid 
succession. The adjusting of the screw and the sliding 
in and out of the secondary coil regulates the frequency 
and the strength of the vibrations. 

The secondary coil is generally constructed of many 
thousands of turns of wire according to the strength of 
E. M. F. desired, the more turns the greater the induced 
electro-motive force; the resistance of so many turns of 
wire is overcome by the great increase in the induced E. M. F. 
The magnetic field and induced current are increased quite 
out of proportion to the resistance by the increasing of the 
number of turns in the coil. 

DYNAMO CURRENTS. 

Continuous Current. — In speaking of the continuous current 
it should be remembered that the current from dynamos 
is not truly continuous, being really a series of overlapping 
waves, but these are, in a good machine, so slight that 
it is usually known as continuous; strictly speaking, con- 
tinuous current is obtained from batteries. 

The continuous current from the main, which constitutes 
a large proportion of the electric supply in commerce, is 
made by converting mechanical power into electrical power 
by means of the Dynamo. 

The Dynamo. — The principal parts of a dynamo are 
the field magnet, the armature, and the commutator or 
collecting brushes. The field magnet is built into the dynamo 
machine and consists of a sort of iron core, built up of a series 
of thin plates insulated from one another to prevent "eddy 
currents," wound with a coil around it which receives 
current from the armature to make it electro-magnetic 
when the machine is working, on the principle of the in- 
duction coil; it also becomes a permanent magnet to an 



86 MAGNETIC FIELD, CURRENTS AND BATTERIES 

extent sufficient to start the dynamo with a few turns of 
the armature. It is so constructed that the armature is 
received into two hollowed-out surfaces of the opposing 
poles of the magnet, the space between the magnet and 
the armature becomes a powerful magnetic field when the 
dynamo is working. 

The poles of this electro-magnet~are permanently set 
north and south. 

The armature is constructed in some dynamos of two 
insulated metallic rings on a shaft which fits into the hol- 
lowed space between the poles of the field magnet so that 
a small space is left between it and the electro-magnet; 
it is also often constructed of an iron core upon which is 
wound insulated conductors so contrived as to fill the 
space between the magnetic poles without touching the 
magnet, as shown in Fig. 26. 



Armatun 

Brush 

Commutator, 
Brush' 

{Magnetic Coil 




Field - 
Magnet 



Fig. 26. — Plan of dynamo. 



On a continuous current dynamo there is a commutator 
which consists of a number of copper bars insulated from 
each other and mounted in the form of a cylinder through 
which the insulated shaft passes, the number of bars cor- 
respond to the number of coils in the armature to which 
they are also attached. 

The Collecting Brushes consist of two copper gauze brushes 
or carbon blocks which are in contact with the commutator, 
set opposite one another on the commutator; when the 
dynamo is in motion the segments of the commutator pass in 



DYXAMO CURRENTS 



87 



rapid succession under the brushes which collect the current 
generated in the machine and conduct it from the dynamo 
by wire connections attached to the brushes. The com- 
mutator converts the alternating current set up by the action 
of rotating the insulated conductor in the magnetic field 
into a continuous current. 

The current which is generated in the armature passes 
into the external circuit and also induces a current in the 
coil around the electro-magnet, rendering it electro-magnetic 
when the dynamo is in motion. 





Fig. 27. — Plan of series-wound 

action. 



Fig. 28. — Plan of shunt-wound 
action. 



There are two forms of dynamo winding, the series-wound 
and the shunt-wound dynamo. 

In the series-wound machine the current passes from 
one brush through the field-magnet coil, then through the 
external circuit back to the other brush. 

In the shunt-wound dynamo the current passes in two 
distinct loops, the first from one brush around the field 
magnet and back to the other brush, the second, which is 
the stronger current, passes through the external circuit 
only; these two are separate currents connected in parallel. 
Shunt-wound motors are the type usually used in dental 
engines, lathes, and motor transformers. 



88 MAGNETIC FIELD, CURRENTS AND BATTERIES 

The dynamo is a reversible machine, that is, if it receives 
current from another source it will itself become a motor 
transmitting force but in the reverse direction. Take, for ex- 
ample, a small dynamo such as is sometimes used to generate 
current to charge accumulators, which is usually driven by 
some form of mechanical power like a water or gas engine, 
if the driving power is disconnected and the current from the 
charged accumulators switched on, the dynamo will work as 
a motor but in reverse direction as long as current is supplied 
to it; in others words, it converts mechanical power into 
electric current, but if supplied with current from another 
source it becomes a motor-transmitting power. 

Alternating Current. — This current from dynamos is one, 
as indicated by the term, which alternates. The flow of 
current rises to maximum in one direction then falls to 
zero and rises to maximum in the opposite direction; the 
time which elapses between the rise in one direction from 
zero to maximum and back to zero is called a semicycle, 

and the time which elapses from 
the rise in the opposite direction 
from zero to maximum and back 
to zero is the other semicycle, so 
that the cycle is completed in the 
time occupied from the rise in one 
direction to the commencement of 
the rise again in the same direction. 
Fig. 29.-Doubie semicurve. These sem icycles correspond re- 
spectively with the passage of the 
coil through the north and south poles of the electro-magnet. 
The time occupied by a cycle in a dynamo therefore depends 
on the rate of the revolutions; in some machines the cycles 
are regulated at 60 cycles per second and are perfectly uni- 
form in number of alternations. The change from one 
direction to another in an alternating machine occupies an 
exceeding short space of time, as is shown by the foregoing, 
and in well-made dynamos is quite regular. 

The current from an alternating machine is often spoken 
of as a sinusoidal current, indicating the curves which would 




DYNAMO CURRENTS 89 

be marked out by an instrument made to register the sine 
curve. 

Suitable transformers are required for whatever the 
source of current to convert the current into a smooth 
wave-like alternating current as used in medical work, and 
is much less painful and more effective for many porposes 
than the sharp, jerky current of a faradic coil. The alter- 
nating current from the main is the only kind supplied by 
many installations in country towns for lighting purposes; 
it is cheaper to install because of the ease and simplicity 
with which it is transformed from one potential to another, 
and also the copper cables used for the mains are much 
smaller than for continuous current. The current passes 
through those cables at enormous volt pressure and is 
transformed when installed, into 100 or 110 volts by a trans- 
former which reduces the voltage and increases the amperage. 

The current from alternating dynamos cannot be used 
as such for charging accumulators, ionic medication, or 
cataphoresis, but as has been stated is used for driving 
motors, heating cauteries, lighting, rotating high-tension 
transformers for x-rays, and for high frequency. 

Transformers. — A continuous current can be transformed 
into alternating by means of a motor working as a dynamo 
(motor-dynamo) and the alternating can be made con- 
tinuous by a similar instrument. The volts can be reduced 
and the amperes increased, or vice versa. It has been shown 
that in the induction coil the electro-motive force of the 
secondary coil depends on the ratio of turns in the secondary 
coil to the primary; if the secondary coil has four times the 
number of turns, the E. M. F. will be approximately four 
times that of the primary, and if it has one quarter the number 
of turns that the primary has, the E. M. F. will be about one- 
fourth that of the primary. At the same time the current 
strength (the amperes) will be affected to the same extent 
in the opposite direction; a high E. M. F. by this arrange- 
ment can produce a very low current strength or a low 
E. M. F. a very high amperage. A transformer can be 
designed to produce a current strength of one ampere at 100 



90 MAGNETIC FIELD, CURRENTS AND BATTERIES 

volts or 100 amperes at one volt, or oan be made to convert 
one into the other. 

An alternating current from the main can be transformed 
by induction into one of low voltage and high amperage; for 
example 2000 volts and one ampere can be transformed into 
100 volts and 20 amperes. 




Secondary Coil 



-Primary Coil 
Electro-magnet' 



Fig. 30. — Alternating current transformer. 



As shown in Fig. 30, the transformer is in the form of 
aii induction coil, the principle is the same, but this is a 
closed-circuit transformer and a much more efficient machine 
than the induction coil. It consists of an iron core, which 
is the electro-magnet, a primary coil through which circulates 
the alternating current and a secondary coil which is in the 
magnetic field and is not wound around the primary but 
around a different part of the magnet and receives the 
induced current. The E. M. F. induced in the secondary 
coil can be regulated by the turns in the coil in ratio to those 
in the primary as lias been explained elsewhere. Trans- 
formers for alternating currents are especially useful for 
cautery, month lamps, hot air, root driers, or syringe. 






DYNAMO CURRENTS 



91 



The principle, as explained, of reducing the volts and 
increasing the amperes places the current for these pur- 
poses entirely in control. By placing a regulating rheostat 
in the secondary circuit the current which has been trans- 
formed may be regulated to suit the kind of cautery or 
lamp or other instrument which it is proposed to use, by 




Fig. 31. — Transformer. 



varying the resistance. The rheostat can be regulated to 
heat a cautery loop requiring 2 amperes or be adjusted to 
increase the current materially to heat a much larger loop. 
Transformers are also used for converting the alter- 
nating current into high voltage and small amperage for 
high-frequency appliances. They are especially adapted 
for this purpose, for the current being alternating, can be 



92 MAGNETIC FIELD, CURRENTS AND BATTERIES 

used from the main without interrupters. For x-ray work 
an alternating current when transformed must be made 
unidirectional before it can be used in the tubes. 

BATTERIES. 

The construction of galvanic cells, their chemical action 
during the production of current, and the methods of con- 
necting them to obtain various current strength has already 
been described. It has been pointed out that Leclanche 
cells are the most practical and most lasting form of voltaic 
cell, because no change takes place within the cell when the 
circuit is open. 

There are many forms of batteries from which a con- 
tinuous current is obtained for most kinds of dental electro- 
therapeutic work. 

A useful battery consists of 18 or 24 small Leclanche 
dry cells which just fit into an oak box made for the pur- 
pose, the cells are connected in series and the current is 
controlled by a crank cell collector by which one or the 
whole battery of cells can be turned on by switching around 
the spring of the crank onto the studs of the collector. The 
current passes from the controller to a sliding shunt rheostat 
and from this to a milliamperemeter from which it goes to 
one of the terminals of the battery, the other terminal is set 
parallel with the former and to these the conducting wires 
are attached for using the current. 

The battery also is provided with a current reverser, a 
very necessary and convenient appliance for ionization. A 
well-fitting cover keeps the battery free from dust, and a 
drawer in the side to keep electrodes and wires handy for 
use. In using the battery all the cells should be switched 
on and the current regulated through the rheostat, which 
is finely graded and turns on the current very gradually 
by sliding the contact shunt along the metal bar. 

A battery should not be used for ionization without a 
rheostat, because the cell selector alone switches on too much 
current at a time, with the consequence that a painful shock 



BATTERIES 



93 



is experienced when each cell is added to the circuit. Most 
of these batteries are made and sold by instrument makers 
with only a collector, but a rheostat should be insisted on if 
good results are desired. 




Fig. 32. — Galvanic battery. 

The current from a battery of 18 or 24 Leclanche cells 
works out according to Ohm's law as follows: Presuming 
the E. M. F. of each cell to be 1.5 volts, which is very nearly 
correct, and the internal resistance (r) to be 3 ohms, with a 
patient in circuit of 1500 ohms' resistance (R) the current 
strength (C) would be 



E. M. F. = 18 cells X 1.5 volts 
R +r R1500 + (r3 X 18) 



0.017 ampere = 17 ma. 



94 MAGNETIC FIELD, CURRENTS AND BATTERIES 

Seventeen milliamperes is a great deal more current than 
is required for ionization of the periodontal membrane, and 
the E. M. F. from such a battery is ample. 

A battery of 24 cells on the same method of calculating 
will produce : 

c = E. M. F. = _ 24 X 1.5 = Q Q22 am = 22 ma> 

R + r 1500 + (3 X 24) 

The current from a voltaic cell battery is a continuous 
and smooth current, much more so than from any working 
dynamo from which there is a certain amount of pulsation, 
although this pulsation is not perceptible to a patient when 
the current is properly controlled by a finely graded rheostat 
and a lamp in circuit on the switchboard. Some dentists, 
however, prefer the battery to the switchboard. 

Home-made Battery. — A dentist should know how to 
construct his own battery. This is a simple matter with a 
slight knowledge of the construction of the parts and the 
path the current should take. A battery which the author 
used for a number of years and was one of the most satis- 
factory he ever possessed was made by himself as follows: 
Place 24 Lelanche dry cells in a small box, which will just 
hold that number, connect the cells in series with red cov- 
ered bell wire, that is, join the zinc of No. 1 cell to the 
carbon of No. 2 and so on until all are connected, that will 
leave the first carbon and the last zinc unconnected, to each 
of these attach a wire two yards long but let the first wire 
be blue and the last be red to distinguish them. The wire 
from the first carbon will be the positive pole and the other 
the negative pole of the battery. Place the box in the left- 
hand corner of the shelf in the lower portion of the cabinet 
and bore two holes an inch apart about 6 inches above the 
cells in the back of the cabinet, through these holes pass 
the two wires. Get a neat polished board of the same 
wood as the cabinet made in the form of a shallow tray 
(J inch deep) , to fit the side of the cabinet which is nearest 
to the operator as he stands by his chair; to this board 



BATTERIES 



95 



first assemble a milliamperemeter, shunt rheostat, current 
reverser, and two screw terminals with the poles marked 
on them. These all have contact screws which pass through 
the board to the tray-like surface at the back where the 
connections with the battery are made with insulated wire 
in the following manner : 




Fig. 33. — Switchboard with parts assembled. 



To the — terminal connect the red wire from the battery. 

To the distal end of the contact rheostat attach the blue 
wire, connect the other end of the rheostat with one upright 
of the milliamperemeter and from the other upright take 
a wire to the + terminal screw. The battery is now com- 
plete but for a current reverser which can easily be included 
if desired but which makes this description a little more 
complicated, and has not been included in the description, 
which it is desired to make as simple as possible. The board, 
when the several parts are connected up, is screwed onto 
the side of the cabinet, and the outfit is a fixture from 



96 MAGNETIC FIELD, CURRENTS AND BATTERIES 

which the current can be switched on at will. Such a bat- 
tery will supply current for ionization, gold plating, and 
many kinds of work for which an ordinary continuous 
current is desired in dental practice. 

The cells last about eighteen months or two years, accord- 
ing to the size. When they are worn out they are easily 
replaced by new ones at a nominal cost. Leclanche wet 
cells can be used in the same manner and they last forever 
with the renewal of the zincs when required, and occasional 
recharging with sal ammoniac, but they take up more room 
and are not as clean as the dry cells. 

This battery can be made on the same principle and 
placed in a portable box instead of being stationary as 
described. 

Cautery Battery. — For cautery and light a battery is 
required which will produce high amperage; for this pur- 
pose the cells are connected in parallel. Four to six large 
cells of the acid electrolyte type so arranged that the ele- 
ments can be lifted out of the chemical electrolyte when 
the cautery is not required, constitute a lasting and service- 
able cautery battery. Cells in parallel act like one large 
cell with large zinc surface, producing current as if con- 
tained in one cell, only the resistance is lessened by having 
several cells and the current is collected more effectively, 
the voltage, however, is affected in the reverse, it remains the 
same as from one cell. This has already been explained. 

The heating of the cautery loop depends on the voltage 
and internal resistance of the battery, and in constructing 
such a battery this must be very low in order that a very 
large current may be taken from it. The current strength 
can be augmented by adding cells in series with each of 
those in parallel, or by connecting two equal numbers in 
parallel and then these two groups in series ; by this arrange- 
ment the current from a number of cells is produced with 
the resistance reduced as if from cells in series. 

Where the main current is installed the cautery from a 
switchboard is much more satisfactory, but the resistance 
must be constructed to control large currents. 



BATTERIES 97 

Accumulator Battery. — For cautery work and lighting 
small mouth lamps, antrum lamps, and working the dental 
engine, this form of battery is one of the most useful. The 
principle of the accumulator cells has already been described. 
For cautery two to six cells are connected in parallel and 
they need not be of large size, the cells have an E. M. F. 
of 2 volts each and the current strength will vary according 
to the capacity of the cells. When formed into a battery 



Fig. 34. — Accumulator battery for cautery 

there should be a sliding contact rheostat to turn on the 
current gradually to suit the size of the cautery or lamp 
that is being used. Many of the small batteries have a 
capacity of 50 ampere-hours which under ordinary circum- 
stances will do service in a dental surgery for a long time. 
The accumulator battery is superior to a chemical cell 
battery for surgical work or light. 



CHAPTER V. 
BATTERY ACCESSORIES. 

Current Collector — Milliamperemeter — Rheostats — Rheophores — Elec- 
trodes — Rheostat for Direct Current from the Main — Resistance for Heavy 
Currents — Alternating Current Transformers — High-frequency Currents. 

Current Collector. — It is usual for most continuous current 
voltaic cell batteries to be constructed with a current col- 
lector. The object of the collector is to vary the number 
of cells to be brought into use at one time to suit the special 
case or to increase the number of cells or collection of cells 
by units as required. A battery containing, say, 24 cells may 
be used with this contrivance so that one or any number of 
cells are switched into circuit by turning the crank handle 
of the collector. 

The current collector consists of a number of metallic 
studs arranged in a circle, fitted in a vulcanite plate which 
covers the cells in the box. The studs are insulated from 
each other and are connected by wires to the corresponding 
cells in the battery in regular order as shown in diagram 
Fig. 35, in which the studs numbered 1 to 8 are connected 
to the positive pole of cells 1 to 8; the negative pole of cell 
No. 1 is connected to a separate stud numbered 0, which is 
connected with the negative terminal of the battery. A 
movable crank handle from the centre of the circle of studs 
is made to fit with perfect metallic contact on the tops of 
the studs over which it can be moved to make contact 
with any of the studs and lead of current from the cells 
corresponding in number to the stud in contact. The 
crank is connected as shown in the diagram with the positive 
terminal of the battery. 



CURRENT COLLECTOR 



99 



The cells being in series it can be readily seen that by 
moving the contact metallic crank to a stud, say No. 8, 
all these cells will be brought into circuit between the termi- 
nals marked + and — , and in the same way when the 
crank is on No. 4 or No. 2 or any stud it brings into the 
circuit the number of cells corresponding to the number 
marked against the particular stud on which it rests. 




Fig. 35. — Plan of current collector. 



In moving the crank from stud No. 1 to No. 2 and so 
on over all the studs it increases the E. M. F. and current 
by the amount corresponding to that of each individual 
cell as the crank moves to each adjoining stud. This increase 
is too sudden for the comfort of the patient in the treat- 
ment of sensitive tissues, such as dentine, pulp, or periodontal 
membrane. 

With this form of current collector the cells which are 
connected with the studs in the first part of the series are 
used more frequently and consequently become exhausted 



100 BATTERY ACCESSORIES 

first, leaving the latter part unused or much less used. To 
obviate this difficulty a more complicated collector has 
been devised, called the double collector, by which any section 
of the battery may be collected. 

Milliamperemeter or Milliammeter. — No battery is com- 
plete without a milliamperemeter, which should be con- 
nected in the path of the current between the rheostat and 
the patient. The value of the milliammeter to the operator 
for determining the current strength can hardly be over- 
estimated, and no one should use the current for dental 
operations without one. This instrument has been greatly 
improved of late by the invention of d'Arsonval, who 
applied the principle of replacing the permanent magnet of 
the galvanometer by a solenoid which produces a magnetic 
field when the current is passed through the instrument; 
by this method the pointer of the needle is made dead beat, 
thus it does not oscillate when the current is first passed, 
as is the case in old forms of galvanometer; its movements 
are controlled by being placed in a magnetic field between 
the poles of a magnet, delicate hair springs are attached 
to the needle through which the current passes, the needle 
deflects gradually from zero, indicating the current strength 
which is passing, and on returning to zero is kept steady 
by the adjustment of the springs. The instrument (Fig. 36) 
works perfectly in all positions, which is an improvement 
on those which are dependent on earth's magnetisms, and 
which therefore require to be set in the magnetic medium. 

The best instruments are provided with a shunt, which 
is a device for lowering the known resistance of the meter 
by a known amount without influencing the magnetic field. 
By connecting the shunt the path of the current is open 
to a conducting wire which allows one-ninth the resistance 
and therefore nine times the current strength to pass, 
thus nine-tenths of the current passes through the shunt 
while one-tenth passes through the instrument. A second 
turn will allow ninety-nine times the current strength to 
pass by contact with a second wire brought into the cir- 
cuit. The plan of the instrument is shown in Fig. 37. The 



MILL1 AMPEREMETER OR MILLI AMMETER 101 

lowest current strength is indicated on the dial by 1, increas- 
ing up to 5 milliamperes. By turning the shunt once the 




Fig. 36 — Milliammeter. 




Fig. 37. — Plan of shunt. 



current is increased by the multiple of 10 and by tinning 
it twice it is increased by the multiple of 100. In ordinary 



102 



BATTERY ACCESSORIES 



dental work it is seldom the first shunt is required and the 
second never. If the current is required for any other 
purpose than ionization, such as gold plating for example, 
where the resistance of the electro-chemical salts in solu- 
tion is very slight compared to the body, it is best to 
remove the milliamperemeter and connect the path between 
the uprights for holding it, with a piece of copper wire, as 
strong current passed through the instrument tends to stretch 
the hair springs and to damage the delicate mechanism. 




Fig. 38.— Voltmeter. 



Amperemeters and voltmeters are also constructed on 
the same principle as the d' Arson val type milliampere- 
meter, and are used in measuring strong currents such as 
current from a small dynamo used for charging accumulator 
battery, and also for testing the voltage of the cells and 
batteries, or the current passing from a switchboard for 
ionic medications. 

Rheostats. — In addition to the current collector it is 
necessary in most dental operations to have a finer gradu- 
ated scale for the increase of the current strength; the 



RHEOSTATS 



103 



switching on of one cell at a time, each cell of 1.5 volts, 
increases the current strength too suddenly in operating 



f ^\ 



+ 



\2A^V^ 



4-6 P ©- 

Fig. 39. — Graphite rheostat. 



§> 




Fig. 40. — Graphite dial rheostat. 

on periodontal tissue or on sensitive dentine, the conse- 
quence is a painful shock each time the crank of the collector 
reaches another stud. To obviate this a rheostat should 



104 



BATTERY ACCESSORIES 



be placed in circuit between the cell collector and the milli- 
amperemeter, indeed, it is unnecessary to have a current 
collector when a proper rheostat is installed. A delicate 
form of rheostat is one of graphite which has a resistance 
of 1000 to 5000 ohms. The current passes through a 
graphite pencil with a sliding contact spring which gradu- 
ally turns on the current by sliding the spring along a bar. 
By this only a fraction of a milliampere of current is allowed 
to pass at a time, and the increase is not detected until 
the current reaches the desired strength. In operating on 
nerve tissue or sensitive dentine a rheostat of this descrip- 
tion is very essential in order to increase the current without 
considerable discomfort. 




Fig. 41. — Wire resistance. 



The most perfect rheostat for resistance of current from 
voltaic cell battery and switchboard, useful for delicate 
work on the pulps of teeth or obtaining sensitive tissue, is 
one shown in Fig. 40. It is constructed of a glass dial which 
turns on a central pivot, on the outer circle of the dial 
graphite is impressed into the irregular etchings on the 
surface of the glass. This is graduated from very fine to 
coarser receptacles for the graphite, in the manner shown 
in the figure. The contact is made with mercury, which is 
let into a slot underneath the dial, and acts as resistance. 
By turning the glass dial over the mercury in contact with 
the graphite conductor the very minimum of current strength 
only is allowed to pass if the dial is slowly turned. The 
full resistance of this instrument is about 20,000 ohms, 
decreasing gradually to 20 ohms. 



RHEOPHORES OR CONDUCTING CORDS 105 

A convenient and effective rheostat for a battery, where 
no current collector is attached or necessary, consists of a 
slate core around which is wound many hundred turns of 
insulated wire, a sliding metallic contact spring is adjusted 
to move over the coils of wire, making contact with por- 
tions of the wire from which the insulation has been removed, 
in such a manner that contact with each turn of the wire 
decreases the resistance by the amount of resistance in the 
length of wire that passes around the slate core, which, 
in this instance, is about 0.1 volt, and the current strength 
is very gradually increased. This form of rheostat is largely 
used on switchboards to reduce the current from the main. 
It requires careful attention in a damp climate, for, should 
the wire oxidize, the insulation is liable to become imper- 
fect, and the current brought on in irregular jerks which 
is uncomfortable to the patients. Should this occur the 
instrument should be discarded. 

Rheophores or Conducting Cords. — Rheophores or conduct- 
ing cords are made of insulated flexible wire finished off at 
each end with suitable metallic connecting ends for attach- 
ment to the terminals of the battery and electrodes. They 
should be of sufficient length to give perfect freedom in 
using the electrodes; two or two and a half yards is a con- 
venient length, and it is best to have two colors, one for 
the positive terminal and the other for the negative. They 
are best made of several strands of fine copper wire twisted 
into a flexible cord which is insulated by cotton covering. 
Cords of a single wire covered with rubber are sometimes 
used, but these are liable to break from being frequently 
wound up and unwound for use, and should a break occur 
when the current is in use, a painful and alarming shock 
to the patient occurs, the possibility of which must be care- 
fully guarded against. This is a possible contingency 
with any conducting cords which should be guarded against 
by using none but the best quality, and seeing that it is 
always in good order. A break of the cord takes place 
most frequently at its junction with the attachment for 
the terminal or electrode, and if not discovered mav lead 



106 BATTERY ACCESSORIES 

to the conclusion that the current has failed, which may 
not be the case; it is then advisable to test the battery to 
decide this point. 

Electrodes. — These are the conductors which convey the 
current to the body. They are the terminals which are 
constructed of some conducting material specially intended 
for the application of the current to the patient. The 
active electrode is that which conveys the current to the 
body, and the indifferent electrode is that by which the 
circuit is completed. 

They consist of all sorts of shapes and sizes constructed 
to suit the particular purpose for which required. In medi- 
cal practice these are very numerous; for dental work the 
indifferent electrode or the one to which the negative pole 
is connected, should consist of some unoxidizable metal 




Fig. 42. — Wrist electrode. 

(or of carbon) which should always be covered with some 
material to prevent actual contact of the metal with the 
body, such as lint or chamois leather or any absorbent 
material, which must be free from chemical ingredient. 
Metal should not be used uncovered to apply electricity to 
the body because it is liable to cause pain and inflict burns 
or blisters on the surface of the skin, due to the electrolytic 
action set up at the surface of contact. 

The indifferent electrode should consist of a flat piece 
of metal about two inches in diameter to which is soldered 
a terminal in the centre for attachment of the conducting 
cord. It should be covered with a pad of lint which can 
be readily removed and renewed. A leather strap with a 
buckle to attach it to the patient's wrist completes the 
wrist indifferent electrode. It is essential to keep the elec- 



ELECTRODES 



107 



trode clean. It should always be applied moistened with 
warm water or a warm saline solution. It should be applied 
firmly to the site of contact and kept moist. 

Some operators prefer to apply the indifferent electrode 
nearer the site of the application of the active electrode. 
In application of the current to parts of the oral cavity, 
when it is desired to place the indifferent electrode near 
to the site of contact of the other electrode, one such as is 
shown in the illustration (Fig. 43), invented by Dr. Lewis 
Jones, should be placed under the chin and held in firm con- 
tact with that surface. This electrode possesses the advan- 




Fig. 43. — Indifferent electrode. 



tage of being readily covered with a new clean cover for 
each patient. It is made in sections which allow of a new 
cover being easily slipped on. Electrodes of this description 
are a little awkward to manage at first but are very good 
for application to this part of the body. 

If the electrode is not large enough or if it does not make 
good contact the current is liable to cause blisters to the 
skin at the site of contact of the indifferent electrode, even 
when a small current is passed. In the case of the hand 
electrode, if the metal is of small size and not grasped firmly 
by the patient, a small, hard, white blister about the size 



108 



BATTERY ACCESSORIES 



of the head of a large pin may appear at some point in the 
palm of the hand, attended with some discomfort to the 
patient, the skin dies at this point and the mark will only 
disappear when the skin is removed a long time after. To 
obviate this occurrence place a carbon electrode, covered 
with a couple of folds of flannel into a glass vessel filled 
with slightly warm water and some sodium chloride, the 




Fig. 44. — Carbon and water electrode. 

patient's hand must be immersed in the water and the palm 
of the hand pressed firmly on the covered carbon conductor 
at the bottom of the glass dish. This is always a com- 
fortable form of indifferent electrode, which patients appre- 
ciate, especially if pain is experienced by contact of other 
forms of metal electrodes. The connecting cord from a 
water electrode should be rubber insulated copper wire. 




^Sj^i 



Fig. 45. — Hand electrode. 



Another form of indifferent electrode quite well adapted 
for ionic medication consists of a nickel-plated metal handle 
which the patient holds. This should have a moistened 
sponge at the open end and should be covered with stock- 
inette or lint moistened with salt and water. It should not 
be of brass or copper as sometimes made, and should be of 



ELECTRODES 



109 



the largest size displayed by makers. This form of electrode 
is preferred by some patients, as they seem to like to hold 
on to something; the epidermis of the palm of the hand is 
thick and not usually sensitive to current of small amperage 
such as is usually required for applications to periodontal 
membrane. 

The chin electrode devised by the author consists of a 
nickel-plated metallic plate which fits under the chin with 
a contact screw soldered to the middle and end pieces to 




Fig. 46. — The author's chin electrode. 



receive an adjustable elastic strap which is intended to pass 
over the head and hold the electrode firmly in place. It 
should be covered with a pad of lint next to the skin, and 
should be moistened with salt water. This form of elec- 
trode for contact on the face is comfortable and useful 
where it is desired to lessen the resistance by having the 
electrodes in close proximity. 

Active electrodes convey the current to the site of appli- 
cation. They consist of an insulated rubber or ebony 
handle with an attachment screw at one end to connect 



110 



BATTERY ACCESSORIES 



the conducting cord to, the other end should consist of an 
interchanging screw piece to receive the particular appli- 
cator required; the electrodes to fit these handles should 
be of platinum, zinc, or copper, and shaped according to 




Fig. 47. — The author's electrode hand piece. 

the requirement of the operation; for pyorrhea pockets or 
gingival trough, spear-shaped metallic points of the metals 
mentioned, 5 cm. long by 2 mm. vide and 1 mm. cross- 
section. These should be interchangeable at the hand 
piece and readily removed for sterilizing. The extreme ends 




Fig. 48. — The author's pyorrhea 
electrodes. 



Fig. 49. 



-The author's root canal 
electrodes. 



should be rounded, as sharp points increase the density of 
the current which makes it painful. The points are flexible 
(except zinc), which permits of them being bent to suitable 
curves for different angles when required to pass to the 



RHEOSTAT FOR DIRECT CURRENT FROM MAIN 111 

approximal surfaces of molars. The shanks of the points 
should be insulated three-quarters of the length to prevent 
the current passing to the lips and cheeks adjoining the 
site of application. (See Fig. 48.) 

For root canals, electrodes of fine copper or platinum 
wire twisted into a coil at one end and straightened out 
for varying lengths of half to one inch in length, the straight 
part for insertion into the root canal, and the coil to receive 
the end of a spear-shaped point attached to the ordinary 
handle, to hold it steadily in position when being used 
(Fig. 49). Iridio-platinum wire electrodes are best for 
treating root canals. 

Copper probes for fistulous tracts of chronic alveolar 
abscesses should be made with this coil at the one end to 
receive an ordinary electrode with which to make contact 
when applying copper ions, as will be described later. The 
thickness of these probes should be 0.5 mm. 

Rheostat for Direct Current from the Main. — The continu- 
ous current from the main is the most convenient source 
of supply of electricity for ionic medication. It is quite 
safe, notwithstanding the high E. M. F., if only ordinary 
precautions are adhered to, and it is not any more painful 
to use than the current furnished by a battery. 

The current from the main must be reduced to very low 
voltage with a minimum output of current strength. This 
is accomplished by suitable resistance interposed on the 
switchboard between the supply and the patient. The cur- 
rent is controlled by passing it through a coil of resistance 
wire which is wound around a core of insulator material, 
like slate. Each turn of wire is insulated perfectly from 
the next, although placed very close to it. Several hundred 
turns of the wire represents a resistance sufficient to reduce 
the current of 240 volts to 0.15 volt. A lamp is also placed 
in circuit which when the current is switched on, assists 
in reducing the current and acts as a guide to indicate the 
presence of the current and a safeguard against sudden 
rise of current by accident to the insulation of the wire 
resistance. 



112 



BATTERY ACCESSORIES 



The principle of the switchboard resistance is explained 
in the diagram; the current passes from A to B through 
the resistance coil. At B a contact sliding metallic spring 
(C) is adjusted on a metal bar over the coil; this moves in the 
direction A over the resistance; the sliding contact is con- 
nected with the + terminal of the switchboard; the end of 
the coil at B is connected with the — terminal; an incan- 
descent lamp is also on the negative side of the board. It 
can be readily seen by the diagram (Fig. 50) that the cur- 
rent must pass through the entire resistance before it reaches 
the contact spring C when it is adjusted at B, and that 




Fig. 50. — Plan of switchboard resistance. 



by sliding the spring toward A the resistance is gradually 
reduced and the current strength increased. The E. M. F. 
when the current passes through the entire resistance is 
only a fraction of a volt; as the spring slides over the coil 
from B toward A it increases the E. M. F. very gradually 
by about 0.1 volt as it passes over each turn of the wire 
coil. A milliamperemeter, which should always be used, is 
placed in circuit between the resistance and the + terminal 
by a connection to the metal bar upon which the contact 
spring C slides. Current controlled from the main by this 
method seldom gives any trouble, as the operating chair 
is usually perfectly insulated, but it must be borne in mind 



RHEOSTAT FOR DIRECT CURRENT FROM MAIN 113 

that in these wire circuits if the negative pole is brought 
in contact with anything connected with earth, when the 
circuit is closed, a severe shock is liable to occur from this 
source, even if the current at the positive pole is reduced 
to minimum by the resistance. For this reason it is dan- 
gerous to use a metallic saliva ejector when using the 




Fig. 51. — Switchboard for ionic medication. 



current in the mouth, for the water might make perfect 
contact with the earth through the metallic pipe connec- 
tions. No water pipe or gas fitting should be touched by 
the operator or patient when the current is being used. 
It is possible for very damp weather to so moisten the 
carpet on which an operating chair rests that imperfect 
8 



114 BATTERY ACCESSORIES 

contact is made with earth and thus to become a source 
of contact when using the current. This can be overcome 
by insulating the chair perfectly by placing the base on a 
rubber mat. 

Current controlled by this form of rheostat switchboard 
(see Fig. 51) is used for all kinds of galvanization and ionic 
medication; the E. M. F. is reduced and the current strength 
brought down to a minimum, and differs from the switch- 
board used for cautery or hot-air syringe, which requires a 
current of high amperage with a low voltage, and which 
cannot be used for ionic medication. 

Resistance for Heavy Currents.— The current which is 
required from a switchboard for cautery light, hot-air 
syringe, water heater, etc., of the type now much used can- 
not be controlled by wire rheostat resistance inserted in 
circuit on the principle of the galvanic switchboard. The 
resistance in series which will permit of strong enough 
current strength to heat a cautery loop would require an 
electro-motive force which would be sufficient to establish 
an electric arc at the moment of breaking the current in 
the handle of the cautery which would destroy the instru- 
ment, or should the platinum loop be overheated and become 
fused when in use, the danger would be serious. The prin- 
ciple of resistance for these switchboards is one which is 
known as the shunt circuit; it consists of two parallel cir- 
cuits: one for the current, which is required for the instru- 
ments, the other acting as a shunt circuit in case of over- 
heating or fusing of any other connection on the switchboard ; 
there are a number of resistance coils of thick wire attached 
to the back of the switchboard which are connected in 
series with conducting studs at intervals, which lead the 
current to the front of the board, where several crank arms 
are attached to switch on the required current for the differ- 
ent instruments for which the particular current strength 
is intended. There is a pilot lamp at the top of the board 
which indicates the presence of the current. The current 
strength of the different instruments is regulated by the 
length, thickness, and number of coils in the wire which 



ALTERNATING CURRENT TRANSFORMERS 115 

form the rheostats at the back of the board, different 
amperage being necessary for different individual instruments 
or sets of instruments. 

When the current is switched on, a large amount of cur- 
rent is constantly passing through the shunt circuit which 
of course is not used, in this there is considerable waste, 
and the current should not be left on the switchboard except 
it is in use. 



Fig. 52. — Transformer for light and cautery. 

Alternating Current Transformers. — It is desirable some- 
times to change the alternating current from the main 
into continuance current, or to transform it into one of low 
voltage and high amperage for cautery or lamp; this is 
accomplished by induction, or motor transformers or by 
rectifiers. 

By an induction coil on the principle already mentioned, 
the current of high voltage can be transformed into one 
of low E. M. F. and high current strength, or by having 
two coils wound on a ring of soft iron, a primary with a 
greater number of turns in the coil than the secondary, the 
current passes through the primary and induces current 



116 BATTERY ACCESSORIES 

in the secondary which is in the magnetic field of the coil. 
Current transformed in this manner is used for cautery 
and light. For producing the opposite effect, that is, trans- 
forming the current into much higher E. M. F., the winding 
of the coils is reversed, the primary with a fewer number 
to turns in the coil than the secondary. Current trans- 
formed in this manner can be used for high-frequency 
apparatus, or if a synchronous commutator in the secondary 
circuit is employed, for the .r-ray work. The switchboards 
are provided with sliding resistance for adjusting the volt- 
age to the required strength. These forms of transformers 
are much used for cautery and light. They are sometimes 
arranged to give two or three different voltages, by having 
two or three secondary windings wound on different parts 
of the iron ring, each having different numbers of turns 
of wire, and induce different currents that are taken to 
different terminals on the switchboard. One coil of thick 
wire and of few turns gives a current of low voltage and high 
amperage for cautery; another of finer wire and more turns 
gives a higher voltage and a certain amperage for lighting 
small lamps; a third of still finer wire and more turns gives 
a current for therapeutic work. Current transformed on 
this principle is readily regulated and answers the purposes 
for which it is intended. 

To transform an alternating current from the main 
into a continuous, a motor which works by the alternating 
current is required. This is made to transmit mechanical 
energy to work a direct current dynamo from which the 
direct current is collected. By a motor transformer a con- 
tinuous current can be obtained of almost any desired 
electro-motive force and current strength suited to windings 
of continuous current engines and lathes or galvanic switch- 
boards, and other dental devices for which a continuous 
current is required. For medical purposes this form of trans- 
former is useful for spark coils, arc lamps, or electro-magnets, 
and it may be used for charging accumulators. 

High-frequency Currents. — High-frequency currents may 
be described briefly as alternating electric currents which 



HIGH-FREQUENCY CURRENTS 



117 



discharge witji oscillations of great frequency. The oscilla- 
tions may amount to millions a second and vary in conti- 
nuity and frequency with conditions of capacity, induction, 
and resistance, in production of the discharge. It is beyond 
the scope of this work to describe in detail phenomena 
of high-frequency discharges. The present efficiency of 
apparatuses for production of high-frequency currents is 
due to the studies and ingenuity of such authors as Sir 



O 



External Armature 



Selenoid 



Spark. Gap 



o 



- ^Internal Arw<%tuye 




Fig. 53. — d'Arsonval's principle of high-frequency apparatus. 

Oliver Lodge, Hertz, Tesla, Elihu Thomson, and d'Arsonval. 
d'Arsonval discovered the present-day principle of the 
high-tension high-frequency coil; he connected the internal 
armatures of two Ley den jars with the terminals of a sec- 
ondary current from an induction coil; to the external 
armatures he connected a spiral of about twenty turns of 
thick copper wire. To the internal armatures he connected 
on an upright two horizontal metallic rods which terminated 
in rounded ends to form a spark gap. He discovered that 



118 BATTERY ACCESSORIES 

on charging the condensers, each time a discharge spark 
crossed the spark gap a high potential current with oscil- 
lations of a high frequency was set up in the spiral attached 
to the external armatures and that this form of current 
could be collected from the ends of the coil (see Fig. 53). 
Many of the modern instruments for producing high fre- 
quency are constructed on the principle of d'Arsonval's 
discovery. The electrical source of energy to work a high- 
frequency apparatus is best obtained from continuous or 
alternating main current supply, but primary and secondary 
batteries can be used. In using current from the main the 
ratio of electro-motive force and current strength must be 
altered, this is accomplished by induction coil current 
interrupters, motor converters, etc., constructed on the 
principles already described. The apparatus consists of 
condensers, spark gap, solenoid, and resonator. 

Condensers consist of two Ley den jars or glass plate con- 
densers constructed on the principle of Ley den jars. They 
are connected by contact with their inner coating of tin- 
foil or metal conductor, with a secondary coil, or high- 
tension transformer or whatever the source of electrical 
energy may be. The spark gap is formed by two adjust- 
able conductors which are in contact with the conductors 
attached to the internal lining of the condensers, the spark 
gap is usually enclosed in some form of covering which 
deadens the sound of the spark, when the discharges between 
the two jars take place. The solenoid is a coil of copper 
wire which is connected to the outer covering of the con- 
densers. It usually consists of about twenty turns of thick 
copper wire. The resonator is made in several forms, and 
consists in one form (d'Arsonval's) of four turns of thick 
wire which is connected at each end to the outer coating of 
the condensers; on the outside of this coil, placed about two 
inches away from it, is a secondary coil of fine wire made 
of a great number of turns over an ebonite cylinder. This 
secondary coil induces currents of higher tension than the 
outer coil of thick wire. 

The several parts of the apparatus are assembled and 



HIGH-FREQVEKCY CURRENTS 



119 



mounted on a small table, or as is the case of a small port- 
able apparatus, in a strong wooden box. The usual type 
of apparatus for medical purposes is shown in the accom- 
panying Fig. 55. The condensers are placed on the lower 
platform of the table and are connected by the inner coatings 




Fig. 54. — High-frequency transformer. 



to the secondary terminals of an induction coil worked by 
motor interrupter and also to the spark gap which is enclosed 
in a box inside which the sparking takes place between the 
metallic knobs which are adjustable to suit the spark desired. 
The outer coatings of the condensers are connected 
through the solenoid, from which the currents are conveyed 



120 



BATTERY ACCESSORIES 



to the patient. The resonator is made of a coil of copper 
wire, which is wound around a frame and placed on the 




Fig. 55. — Combined high-frequency apparatus. 

top of the table. These two are connected in different 
ways according to the make of the apparatus; some have 
adjustable contacts. 



HIGH-FREQUENCY CURRENTS 



121 



A milliampere meter of the hot wire type (Fig. 56) is 
usually connected between the patients and the solenoid, 
or the resonator of the high-frequency apparatus. 

High-frequency currents conducted from the solenoid 
to the body are of great magnitude. d'Arsonval has shown 
by experiment that an incandescent lamp placed in series 
between the instrument and the patient, so that the current 
must flow through the lamp before reaching the patient, 
will glow brightly, yet no unpleasant sensation is noticed 
if the electrodes are firmly grasped. It would be impossible 
to pass a similar current without serious effect on the body. 




Fig. 56. — Hot wire milliampere meter. 



In general electrification of the body by high-frequency 
currents different methods are adopted for passing the 
current to the body; by direct conduction from the ends of 
the solenoid; by conduction from one end of the solenoid 
with the other end connected to a conductor placed in 
proximity but not touching the patient; and by auto- 
conduction, which consists in placing the patient in spiral 
wire enclosures large enough to completely enclose him 
without touching him, the current passing through the wire 
enclosure or solenoid is transmitted by induction. 

In the use of high-frequency currents for local applica- 
tion in dental treatment a modified apparatus is required. 
This has been carried out in one form by what is known 



122 



BATTERY ACCESSORIES 



as the Tesla transformer principle, which requires no motor 
interrupter. The apparatus is connected to the main, con- 
tinuous or alternating current, by a wall plug, the current 
passes through an arrangement of induction coils and a spark 
gap which regulates the potential and frequency. The 
current is conveyed to the mouth of the patient by a vacuum 
glass electrode which when in poor contact with the tissues 
produces slight heat, and if held a slight distance away 
produces a small brush spark. The sparking gap is only 




Fig. 57. — Victor Gem high-frequency apparatus. 



two or three inches wide, which produces high-frequency 
currents of sufficient amperage for treatment of oral tissue. 

Such an apparatus is shown in the cut. It is of American 
make, called the Victor Gem high-frequency coil, Messrs. 
Ash & Sons being the English agents. Glass vacuum 
electrodes made to shapes adaptable to treatment of the 
gums, supplied with this outfit, are admirably suited for 
the purpose; a wire conductor passes through the glass, 
conveys the current and establishes connection between 
the interior of the electrode and the conductor. 



CHAPTER VI. 
DENTAL ELECTRICAL APPLIANCES. 

Motors — Electric Engines — Electric Lathes — Switchboards — -Accumu- 
lators — Direct Resistance — Motor Converter — Electric Hot-air Syringe — 
Electric Sterilizer and Hot-water Apparatus — - Foot Warmer — Electric 
Furnaces — Pyrometer — -Electric Gold Annealer. 

Motors. — [Motors for operating room engines, laboratory 
polishing and grinding lathes, ventilating fans and com- 
pressed-air pumps, are usually constructed of a pair of 
fixed electro-magnets for generating a magnetic field, an 
armature which revolves in the magnetic field, and a con- 
trolling resistance for regulating the speed. 

The electric field magnets consist of two separate coils of 
insulated wire wound in opposite directions and fitted on 
shaped soft-iron cores or pole pieces. The armature is the 
driving force of the motor and consists of a number of coils 
of Avire wound in slotted plates fitted to the spindle. The 
ends of the coils terminate at a commutator, which is com- 
posed of a number of copper segments insulated from each 
other and from the steel spindle to which it is fixed. On the 
surface of the commutator a pair of brushes make contact 
and are held in position by suitable holders and springs, 
which hold the brushes firmly against the surface of the 
commutator as the armature revolves. These brushes carry 
the current supply to the armature. 

The surface of the commutator should be kept smooth and 
clean and sufficient tension given to the brush springs to keep 
the brushes from jumping as the armature revolves, not 
enough, however, to cause undue Avear betAveen the surfaces 
of the brushes and the commutator. To clean the com- 
mutator a piece of soft cloth should be firmly AATapped around 



124 DENTAL ELECTRICAL APPLIANCES 

the tip of the forefinger, moistened with spirit and pressed 
onto the surface of the revolving armature. This can be 
done with ordinary care, without fear of shock. The motor 
should then be stopped, the brushes should be lifted and the 
contact surfaces carefully wiped. Should the brushes be of 
metal gauze, care should be taken not to fray the edges, as 
frayed edges cause sparking at the brushes, which must be 
prevented, because it burns the surface of the commutator 
and makes it uneven, and may later on lead to a burn-out 
of the armature. If the surface of the commutator is at all 
rough, or blackened carbon brushes are used, a piece of fine 
sand or cuttle fish paper should be held flat on it as the 
armature revolves, until a smooth, bright surface is obtained. 
Any dust on the brushes and commutator should be afterward 
carefully wiped off. Emery paper should not be used. 

Motors which have carbon brushes should have the sur- 
faces of all internal parts wiped clean from carbon dust, 
since if this is allowed to deposit it may in time cause a 
short circuit and seriously damage the motor. 

The bearings should be sparingly oiled and every care 
should be exercised not to allow surplus oil to run over the 
insulating material of any wires, as oil destroys it by its 
action on the rubber. 

Careful attention to the above-mentioned points will 
insure long life to the motor and often save an expensive 
"burn-out." 

Electric Engines. — There are a number of electric engines 
on the market, chiefly of American and English manufacture, 
the original being the well-known "Columbia," made by the 
Ritter Dental Manufacturing Co., of Rochester, U. S. A. 
The motor is enclosed in two metal hemispheres and hangs 
by a circular cord from a suitable wall bracket with pulleys, 
and is about -£§ horse power. The suspension cord consists 
of four feed wires, two for the field magnets and two for the 
armature. These are twisted together and covered with 
insulating cotton and silk, built into a neat circular form. 
The cord passes over the two pulleys and down the wall on 
which the bracket is fixed, and has attached to it a lead weight 



ELECTRIC ENGINES 125 

to counter-balance the motor and to admit of it being raised 
or lowered with a light touch of the operator's hand. The 
cord finishes at a small contact plate or resistance box which 
is fixed to the wall, usually from one to two feet from the floor, 
and fitted with a pair of terminals for connecting the engine 
to the electric supply mains, by means of ordinary twin 
flexible wire; it also acts as a connecting plate for the ends 
of the floor cable which leads from the foot controller. This 
cable contains four to eight separate wires. 

The resistance usually consists of a number of coils of 
wire, wound on some suitable insulating material and 
enclosed in a separate box or in the foot controller. These 
coils have wires which lead to copper contacts in the con- 
troller, over which pass spring contacts, worked by means 
of a foot lever. The contacts control the entire working of 
the motor — starting, stopping, speed regulation, etc. 

The controlling lever of the foot switch generally has a 
free swinging movement and requires to be held in position 
with the operator's foot while the motor is in action. Some 
manufacturers fit a locking device which holds the lever 
in any desired position and is released by a slight tap with 
the foot. The locking device is not so safe as the free lever, 
as a few seconds may elapse in releasing the lever, whereas 
with the free swinging lever the withdrawal of the foot 
instantaneously stops the motor. 

Foot controllers should be opened occasionally and care- 
fully cleaned, especially the surfaces of the various contacts. 
After cleaning, the surfaces should be smeared with a very 
slight film of oil, to prevent wear of the two copper surfaces 
by friction. Too much grease will cause loss of power in the 
motor, on account of its insulating properties. 

Other designs of engines found in catalogues of the dental 
manufacturers and supply houses are all practically con- 
structed as described above with various modifications, 
chiefly in the controller; some are fitted with the flexible 
cable, and others with the all-cord arm for receiving the 
hand-piece and instruments. 

The all-cord arm is superseding the flexible cable arm to 



126 DENTAL ELECTRICAL APPLIANCES 

a very large extent, although the cable arm possesses the 
advantage of adaptability, particularly in the wrist, and this, 
from the operator's point of view, is a great convenience. 

Electric Lathes. — These are more simple than engines for 
operating rooms, and usually consist of a motor, which 
varies from 2V to £ horse power with suitable spindles. 
The motor case is completely closed, ventilation holes not 
being necessary, as these lathes are not, as a rule, run for 
long periods, and do not generate much heat in the coils; it 
is also important that grit and moisture from the polishing 
brushes and grinding wheels be excluded from the working- 
parts. The armature spindle extends on each side of the 
motor beyond the bearings for about an inch, and on these 
ends the chucks are fixed; they are very slightly tapered 
while the chucks are correspondingly tapered. Chucks fitted 
in this manner are held very securely on the spindle, and can 
only be removed by direct pressure along the spindle, such 
pressure being usually applied to the outside of the bearings. 

Switchboards. — Various forms of switchboards have been 
specially designed and manufactured for dentists' use. 
These provide methods for supplying and controlling both 
high and low voltages by means of suitable switches, safety 
" cut-outs," regulating rheostats, etc. 

These switchboards are usually made up in panel form 
arranged for attachment to the wall or cabinet, within easy 
reach of the operator. The panel is generally either of marble 
or enamelled slate fitted to a metal frame, and contains the 
necessary connections, wire resistances, etc. 

The high-voltage circuit, as a rule, has four or six terminals 
to which flexible wires can be attached for the engine, 
lathe, fan, gold annealer, reflector, sterilizer, hot-water 
apparatus, etc., or to any appliance which is made to work 
with the same electro-motive force as is possessed by the 
particular current supply available. Each terminal is 
controlled by a quick break switch, and a "cut-out," and 
the operator can switch the current on to or off from any 
of these appliances, without moving from the chair side. 
It is important that the fuse wires in cut-outs should be of 



SWITCHBOARDS 127 

the correct size to carry the amperes required by each 
apparatus; heavy fuses for low amperage appliances are 
practically useless. Fuses are intended for the purpose of 
protecting the appliances in use and preventing them 
being burned out or injured by a sudden increase of current, 
due to some defect or short circuit. 

The approximate sizes of fuse wires required for high 
voltages (200 to 250 volts) are as follows : 

For motor, engine, lathe, fan, reflector, etc., 1 ampere. 

For Mitchell's low-fusing inlay furnace, annealer, atomizer 
and tumbler heater, 2 amperes. 

For high-fusing inlay furnace, sterilizer, and hot- water 
apparatus, 3 to 5 amperes. 

Low-voltage circuit is required for such appliances as 
cannot be used from the full voltage of the current supply, 
as, for example, mouth examining and antrum lamps, root- 
drier, cautery, gutta-percha heating instruments, hot-air 
syringe, etc. These usually require a current of from 2 
to 12 volts, and from \ ampere to 8 amperes. 

When the current is alternating, the low-voltage circuit 
is easily attainable from a suitable design of transformer, 
fitted either on the front or back of the switchboard panel. 
This circuit consists of primary and secondary coils wound 
on a soft-iron core of convenient shape, and a regulating 
rheostat for graduating the voltage and amperage in regular 
and gradually increasing ratio. The low- voltage current 
used is taken from the secondary coil which is quite separate 
from the main current supply. 

When the current is continuous, especially if it be of high 
E. M. F. (200 to 250 volts), the difficulty' in reducing the 
E. M. F. to 2, 4, 6 volts, etc., and at the same time obtaining 
a graduated amperage at these low voltages, is very much 
greater, and represents a heavier loss of current than when 
the current is alternating. There are various methods 
employed for this purpose. The three most practical ones 
are those used by the various manufacturers, viz., accumu- 
lators, direct resistance, and the motor converter. 



128 DENTAL ELECTRICAL APPLIANCES 

Accumulators. — A two-cell accumulator which gives a 
little over 4 volts when fully charged, is connected to a pair 
of terminals on the lower part of the switchboard. By means 
of wires behind the board the cells are connected to a resist- 
ance coil with a sliding contact, which is connected to three 
or four terminals on the edge of the board. The flexible 
wires for the mouth lamp, cautery syringe, etc., are connected 
to these terminals. All these instruments are constructed 
to work on from 2 or 4 volts. The current from the cells 
passes through the resistance and by slowly moving the 
sliding contact from one end of the resistance toward the 
other, the current can be very gradually increased until 
the correct strength is obtained to light the lamp or heat the 
instrument required for use. 

The cells are usually charged through high candle-power 
lamps fitted on the upper part of the board, which act as 
resistance to the high voltage of the current supply. The 
lamps should be of the same voltage as the lighting or 
power current used. The lamps are switched into the 
accumulator circuit by means of a double pole-switch, so 
that when the current is being taken from the cells the 
high voltage supply can be disconnected; this prevents the 
possibility of either operator or patient receiving a shock, 
which might happen if a single pole switch is used. 

A voltmeter is attached for detecting the lowering of the 
power in the cells; it is most important to keep these fully 
charged, if the E. M. F. is allowed to drop below 2 volts, 
the acid in the cells acts on the plates and quickly destroys 
them. 

The method of reducing the direct current by accumulators 
works satisfactorily with a little care in keeping the cells 
always charged to their full capacity. The resistance lamps 
produce considerable glare during recharging and are in that 
way objectionable. 

Direct Resistance. — In this form of resistance the back 
of the switchboard is fitted with coils of resistance wire, or 
other resistance material in the form of metal plates, the 
wire being of the correct gauge and length to reduce the 



DIRECT RESISTANCE 129 

high- voltage supply to 2 volts and a fraction of an ampere. 
For voltages of from 200 to 250 volts, coils of thick iron wire 
of considerable length, with ample air space, are attached 
to the back of the slate slab. The current in passing 
through the wire resistance generates considerable heat which 
is dissipated in the ventilation spaces provided. 

At regular distances along the main resistance, short 
wires are attached and connected to a series of studs on 
the switchboard — some thirty or more in number. A 
sliding contact passes over these studs and reduces a por- 
tion of the resistance at each step, thereby gradually in- 
creasing the strength of the current to the terminals which 
are connected to the circuit for the use of the cautery, 
syringe, root-drier, etc. As the resistance is reduced the 
amperage rises in proportion, and also the temperature of 
the wire. They are at their maximum when the cautery is 
in use; this instrument generally requires a current of from 
6 to 8 amperes and E. M. F. of 2 to 4 volts. 

Where a cautery is used from currents of 200 volts upward, 
it is often considered advisable to fit the heavier resistance 
wire into a separate frame, suitable for standing on the floor, 
in order to reduce the heat given off at the back of the board. 

This arrangement is not dangerous or as wasteful as may 
be imagined, for these low-voltage appliances are, as a rule, 
only required occasionally during an average day's practice, 
and then only for very short intervals, probably only for 
two or three minutes at a time, it will readily be seen that 
the current is not passing through the resistance long enough 
to produce much heat or to waste any great quantity of 
current. With ordinary care no trouble may be anticipated, 
but it is advisable to have a lamp fitted on the board to act 
as a signal. This lamp only lights when the resistance cir- 
cuit is in use; the light will then always warn the operator 
that the current is still passing, should he forget to switch 
off the resistance after using the cautery, syringe, etc. 

With the direct resistance method one pole of the main 
supply is always connected to the low-voltage terminals, 
hence it is possible to receive a shock if the handles of the 
9 



130 DENTAL ELECTRICAL APPLIANCES 

appliances used are not perfectly insulated. The advantage 
of the method is that so long as the main current is avail- 
able the supply is always certain, and the operator is saved 
the necessity of constantly watching the apparatus, as is 
necessary when accumulators (which require regular charg- 
ing) are used. 

The Motor Converter. — An alternating current is the most 
satisfactory for producing low voltages; when a fairly 
heavy amperage is required it is readily transformed with 
very little current loss or heat and with absolutely no risks 
of shock from the high-voltage circuit. 

When a continuous current has to be used, the safest 
and best method of producing the low-voltage current is by 
means of a motor converter. This consists of an ordinary 
continuous current motor with alternating current collect- 
ing rings and brushes fitted to the armature at the end 
opposite to the commutator. This combination when run 
by the continuous current acts both as a motor and a dynamo, 
an alternating current is given off from the collecting rings 
of the armature, which is conducted by a pair of wires to a 
primary coil of a small transformer fitted to the switchboard. 
This produces a low-voltage current which passes through 
the secondary coil of the transformer, from which it is con- 
veyed by means of a sliding contact. A graduated current 
is by this means obtained to suit voltage and amperage of 
the various instruments. 

The only disadvantage of the motor converter method is 
that a small motor is necessary, in addition to the switch- 
board, but all trouble of attending to accumulators, the 
need of heavy resistance coils, and the unavoidable heating 
are done away with; moreover, all risk of shocks to either 
patient or operator is entirely avoided. 

If desired, the motor can be put out of the way in a box 
or cupboard, or it may be placed in another room and con- 
trolled by a switch on the switchboard. In addition to the 
special work for which it is intended it can also be used 
in the operating room as a lathe, when not employed for 
generating the low-voltage current. 



THE MOTOR CONVERTER 



131 




Fig. 58. — Switchboard. 



132 



DENTAL ELECTRICAL APPLIANCES 



By this method the low-voltage circuit only is converted 
to alternating current; the high- voltage continuous current 
circuit remains unaffected and always available for motor 
power. 

A modern switchboard is shown in Fig. 58. This is sup- 
plied either with the direct resistance or with the motor 
converter. When the motor converter* is employed the 
motor is fitted for use as an operating-room lathe and thus 
answers a double purpose. 




Fig. 59. — Mouth lamp from main. 



Electric Hot-air Syringe. — This usually consists of a 
platinum coil fitted inside a glass tube, protected by a 
metal sheath which is perforated, to admit of the coil being 
seen, so that the current can be adjusted to produce the 
proper degree of heat. The syringe is adapted for use with 
compressed air. The electric current and air supply are 
switched on or off by a single movement of the switch 
which is fitted in the handle. The current required for 
working it is 6 volts and from 4 to 6 amperes. 

A syringe is made which can be Worked without any 
resistance direct from any current of high electro-motive 



FOOT WARMER 133 

force. A separate switch with a valve controls the current 
and air supply. The current, which is only in circuit for 
about half a minute at a time, generates sufficient heat in 
the coil for three or four minutes' use. 

Electric Sterilizer and Hot-water Apparatus. — A form of 
sterilizer consists of a water container made of brass which 
is pressed from one piece, it has therefore no seams or soldered 
joints. The heating element is composed of a special alloy 
made into a flat wire which is wound on an iron plate insulated 
with mica. Two of these elements are fitted in the bottom 
of the water container to which they are firmly clamped 
and connected with wires to three terminals which are fixed 
to the base. Connectors provided with triple flexible wires 
admit of four different temperatures. 

The sterilizer is so designed that, in case of an accidental 
fusing of the heating elements, the base can be removed, 
the elements taken out and repaired or replaced by new ones. 

Care should be exercised with sterilizers or any form of 
electrical hot-water heaters, not to allow the containers to 
become dry when they become overheated and destroy the 
heating elements. 

A form of sterilizer, of American manufacture, known 
as the "Monarch" Visible Sterilizer, is made of cast alumi- 
nium which is strong, light, and easily cleaned, the glass 
vessel is made of specially annealed triple lead glass which 
the manufacturers claim will not crack with ordinary use. 
The heater is in the form of an immersion element made of 
cast brass, in which a special form of wire is fitted, wound, 
and insulated in such a way that it will stand constant 
use without risk of fusing, provided the current is not 
switched on except when the element is in the water. When 
not used for sterilizing purposes the glass vessel can be 
employed as a heater for the atomizer bottles. 

Many forms of electrical jugs, kettles, and tanks are made 
for heating and boiling water in the operating room, which 
are constructed on the principle described. 

Foot Warmer. — The foot warmer consists of a thin metal 
case which encloses a wire resistance designed not to reach a 



134 



DENTAL ELECTRICAL APPLIANCES 



high temperature, even though the current be left on for 
a considerable time. It is covered with carpet which gives 
it a neat appearance, and the heat generated is just comfort- 
able to the feet. 

Electric Furnaces. — The electric furnace is made of a 
fire-clay muffle wound with platinum or iridio-platinum wire 
which is capable of withstanding very high temperature 
and produces heat for fusing metals or porcelain bodies. 




Fig. 60. — Pelton electric furnace. 



Platinum, although capable of resisting great heat, will 
occasionally become overheated and the fusing of the coil 
destroy the furnace; the principal cause of this is switching 
on current too suddenly. The wire is w T ound in grooves 
on the outer surface of the muffle which provide perfect 
insulation when expansion takes place during heating; a short 
circuit would cause fusing of the wire. 

The wire used in wiring a muffle varies in diameter and 
length according to the voltage of the current to be used and 



ELECTRICAL FURNACES 



135 




136 DENTAL ELECTRICAL APPLIANCES 

the temperature required. Very accurate calculations are 
necessary to determine these points and to ensure correct 
resistance in heating the wire to the right temperature with- 
out overheating, or, on the other hand, not heat the furnace 
sufficiently. 

Pyrometer. — The pyrometer is used for registering the 
temperature generated in a furnace. It is connected by a 
thermo-couple to the muffle. The fusing-point of the metal 
or porcelain body being known, the required heat is registered 
on the dial of the pyrometer and fusing accomplished without 
opening the furnace. 

The pyrometer is a very delicate instrument and some- 
what expensive. It works independently of the ordinary 
electric current supply and develops a thermal-electric 
current in its own circuit. The thermo-couple consists 
of two pieces of wire, platinum, and iridium, which are 
insulated from each other, except at their extreme ends. 
Two of the ends are fused together while the other two have 
flexible wires attached for connecting them to the terminals 
of the pyrometer. The fused part is fitted into the furnace 
muffle and the action of the heat generates the thermal 
current which passes along the flexible wires and acts on 
a small coil in the pyrometer which deflects the needle. 

Electric Gold Annealer. — The electric annealer is made 
of a fire-clay slab three inches square, divided into sections, 
wound underneath with platinum wire, and fitted to a small 
stand with a metal cover. Pelton's annealer is fitted with 
a regulating resistance which regulates the temperature. 



CHAPTER VII. 
THE X-RAYS OR ROXTGEX RAYS. 1 

X-ray Apparatus — Dental Radiography — The Uses of the X-rays in Den- 
tistry — Development of Radiographs. 

The Rontgen Ray Apparatus. 1 — X-rays are produced by 
passing an electric spark, usually from 10 to 18 inches long- 
in air, from an induction coil or other electric machine, 
through a special glass tube having a high vacuum, and 
enclosing terminals known as the cathode and the anti- 
cathode, which latter is frequently joined to another called 
the anode. 

Cathode rays are thus produced in the tube, which striking 
a target (anticathode) made of metal of high atomic weight 
and fusing-point, give off the .r-rays in the tube, which pene- 
trate the glass sides of the tube on the same side as that 
of the anticathode struck by the cathode stream. 

X-rays thus produced in the air have the power of pene- 
trating all substances more or less, according to their strength 
and also in the same ratio as the atomic weight or density 
of those substances. They also have the power to fluoresce 
certain substances, as barium platino-cyanide, potassium 
platino-cyanide, tungstate of calcium, etc. The .r-rays also 
affect photographic plates of all kinds more or less, according 
to the thickness and quality of the emulsion, the effect being 
produced in all probability by bombardment of the .r-ray 
particles. 

Special .T-ray plates are made and at the present time 
the Ilford are the best. Of the photographic varieties, the 
"ordinary" speed are usually better than the "rapid," but 
again the writer has obtained excellent results from such 

1 By Mr. Charles A. Clark, of London. 



138 THE X-RAYS OR RONTGEN RAYS 

fast emulsions as Paget 5X Lumiere's Sigma, and Extra 
Rapid, though all of these require a longer exposure than 
the special ;r-ray plates mentioned. 

At the present time for obtaining the current for the 
x-rays the coil is the most usual instrument. At first these 
were made to give a spark of a certain length only, but now 
the great aim is to obtain not only length of spark but as 
large a current as possible. Different makers have different 
methods of building coils, and a general description only will 
therefore be given. 

The coil consists essentially of (1) an iron core; (2) primary 
winding, and (3) secondary; between these two latter there 
is a thick ebonite tube. In the early days the iron core was 
made rather too small ; it is now made of bundles of thin, soft- 
iron wire or of soft-iron laminse. 

Outside this core is the primary (duly insulated from 
the core) of thick, double, cotton-covered copper wire. 
Originally this was made in two layers, the wire being 
wound to the end and then back again on the first layer. 
Now it is made in six or more parallels, to which the primary 
current can be adjusted. 

The whole of the primary and the core are placed in the 
ebonite tube, which is filled up with an insulating medium, 
usually hard paraffin. 

Outside this is the secondary winding of thin, double, silk- 
covered wire. This wire is of increasing thickness toward 
each end of the coil, so as to obtain as much current as 
possible. 

Some make this secondary in vertical sections of f inch 
thick to build up the coil. One maker makes this secondary 
sectionless, that is, only one layer of wire between sheets 
of paraffin paper. This has to be wound in a horizontal 
position, a small roller preventing the wire overlaying. An- 
other maker winds the secondary from end to end, always 
keeping to the proper number of turns and over each layer 
of wire, sheets of insulated paper are laid. Over all is laid a 
thin sheet of ebonite, and the ends of the coil covered with 
thick ebonite disks. 



THE RONTGEN RAY APPARATUS 139 

Coils are made to suit the voltage that is to be used, 
usually from the main up to 250 volts. They can also be 
made for as low a voltage as 20 volts, but probably the 
most suitable is 100 volts. 

The current is direct but interrupted, and its action is 
to produce a secondary current at a very high potential; 
but compared with the amperage of the primary, of a very 
small milliamperage, this latter being from J milliampere 
up to 25 or 30 milliamperes, which would be considered a 
heavy secondary discharge. 

A condenser made of sheets of tin-foil separated by a 
dielectric is necessary to obtain the required length of 
spark and current, except when the electrolytic break is 
used, when it is "cut out." The action is to take up cur- 
rent produced at the "make" of the interrupter so that it 
is discharged at the "break" of the interrupter, thus greatly 
increasing the spark, as the current produced at the breaking 
of contact is the one desired. So that when the inter- 
rupter "makes" a current flow in one direction, but on 
breaking it flows in the contrary direction and a surging 
current is therefore set up. 

At the present time coils are made of such power that it 
is possible to obtain perfect radiographs by means of a 
single flash with the aid of an intensifying screen; such are 
the Dessauer Coil and Siemens. 

The Dessauer consists of a very large coil, the whole of 
which is immersed in oil as an insulator. No interrupter 
is required, but a fuse fitted in a cartridge is in circuit with 
the primary. On switching on the current (about 80 
amperes) the fuse (the thickness of which is properly gauged) 
bursts, and to prevent arcing is damped down. Hence a 
"breaking" spark is obtained. The weight of this apparatus 
is about half a ton. 

The Siemens single-flash apparatus is a very large coil 
and the primary current is gradually let in and when at its 
maximum is suddenly broken, the spark (to prevent arcing) 
being blown out by compressed air. The advantage of a 
single flash must be obvious. The rapidity is such that 



140 



THE X-RAYS OR RONTGEN RAYS 



there is no blurring through movement, and also the anti- 
cathode being struck only once, instead of many times 
and never in the same identical spot, makes for perfect 
definition. 







Fig. 62. — The "Snook" Rontgen apparatus. 



But the Snook Rontgen apparatus is an entirely new 
departure and consists of a high-tension transformer, the 
alternating current of which is rectified by a high-tension 
commutator or reversing switch driven by the rotary con- 
verter which, if running from a continuous main, converts 



THE RONTGEN RAY APPARATUS 141 

the current from continuous to alternating. The practical 
result is a unidirectional current which is ideal for working, 
preventing gray negatives and also preserving the condition 
of the .r-ray tube. It is also possible by means of a switch 
to obtain any desired current from 1 milliampere to 60 
milliamperes. 

The Wimshurst Influence Machine consists of one or more 
pairs of glass (covered with a varnish of shellac) or ebonite 
plates on a single axle. In each pair the plates revolve in 
opposite directions and may be supplied with sectors or 
without. This machine gives a comparatively long spark 
according to its size, with a very small amount of current 
so that the Wimshurst is termed a static machine; but in 
America there are some Wimshurst's built on a vertical axle 
which will give as much as 15 milliamperes. The use of 
static machines in this country is not wholly satisfactory 
owing to the humidity of the climate. To overcome this 
they are sometimes placed in glass cases, but then again these 
have their disadvantages. The static machine with all its 
faults has advantages over coils in that (while running) the 
current is absolutely unidirectional; is excellent for radio- 
scopic work and — probably owing to the small amount of 
current — does not produce .r-ray dermatitis. It is, however, 
of little use for radiographic work owing to the length of 
exposure. 

Static currents possess therapeutic value in some cases. 

Primary Current. This is now usually obtained from 
the main chiefly for these reasons: convenience, increased 
voltage, and quantity of current accumulators requiring so 
much attention as well as being an expense. 

The supply from the main may be, however, continuous or 
alternating, and if the latter it must be rectified, i. e., made 
continuous. 

Continuous current in different parts of the country, 
unfortunately, may be supplied in various voltages. Also 
it is generated in some districts at as high voltage as 480 
volts, which is reduced for lighting and other purposes in 
mains of 240 volts bv means of the three-wire svstem. 



142 



THE X-RAYS OR RON T GEN RAYS 



This consists of having between the positive and negative 
wires a neutral wire, as shown by the following diagram: 



480 



2q 



2i0 



2m 




Fig. 63. — Diagram of three-wire system. 



Now if current is taken from the mains A and B the volt- 
age will be 480. But if a neutral main wire (C) is used (elec- 
trically) between A and B, and connections made between 
A C and B C then will the current between A C and B C be 
reduced one-half — 240 volts. It is also necessary that an 
equal current is available on both sides when a large and 
sudden demand is made, as in switching on 20 or 30 amperes. 
Alternating current must be rectified, and probably the 
most satisfactory method is by means of a motor gener- 
ator, which consists of an alternating motor of the voltage 
of the main coupled to a continuous current dynamo of 
the requisite voltage and output in current. 



THE RONTGEN BAY APPARATUS 143 

These are made so that the sudden switching on of a 
large current to the coil is possible. 

A very efficient rectifier is the Nodon valve, and it is 
possible to work a coil with it, but it is not so good as the 
above. It is made of an aluminium rod and a sheet of iron 
immersed in a solution of phos. sodii. This allows current 
to pass in one direction only, the reverse being dissipated 
in the solution as heat. 

If current from the main is not obtainable then a suffi- 
cient number of accumulators and of such a size as will 
give the required current must be used. The writer has 
always found the Lithanode very reliable and portable as 
well as giving a large output. These can be easily charged 
from the main through a lamp resistance — of course, recti- 
fied previously if the current is alternating. If mains for 
charging are not available, then a small gas engine or motor 
dynamo (direct shunt wound) should be used. Or, again, 
if the latter is not to be had then they can be charged by a 
battery of gravity (CuSo 4 ) primary cells, bearing in mind 
that each primary cell has a pressure of only about 1 volt, 
whereas each accumulator cell has a pressure of about 2 
volts, and also it is necessary to have a greater voltage in 
the primary battery than in the accumulators by about 
1J to 1 volt. 

The amount of current given off from the primary cells 
is small. 

If the a>ray worker cannot have any of the foregoing 
means of obtaining primary current, then primary batteries, 
such as Grove's or bichromate, are the only resort, but 
these give the maximum amount of trouble and annoyance 
apart from greater expense, so much so that the writer 
would strongly advise them not to be used, 

Interrupters or Breaks. — The interrupters for break- 
ing the current in the .r-ray coil may be divided into (1) 
mechanical and (2) electrolytic. 

The Hammer Break was the first and acted in the same 
manner as the hammer of an electric bell. It is now quite 
obsolete. 



144 THE X-RAYS OR RONTGEN RAYS 

The Vril was an improvement on the hammer break in 
allowing more current to pass into the primary coil, but it 
was somewhat slow, and noisier than the hammer. 

The Dipper Break consists of a wire worked by an electro- 
motor which dips in and out of mercury, thus making and 
breaking the current. The mercury is contained in a glass 
vessel with either methylated spirits, paraffin or gas as an 
electrolyte. In working, the mercury is apt to become foul 
by reason of a mud which forms, although if an iron vessel is 
used much less mud results, consequently less cleaning is 
necessary. To recover the greater portion of mercury from 
this mud it is advisable to place it in a large dish to allow 
evaporation of the electrolyte. No mud is formed with coal 
gas as electrolyte. 

This break is only suitable for low voltages — say 20 to 
50, but it can be used up to 100 and will pass a current up 
to 20 amperes or so. It is somewhat noisy to use. Either 
large or small currents are obtained by adjusting the vessel 
so that the dipper will go more or less deeply into the mer- 
cury. At starting it is necessary to speed up the motor 
before switching on the primary or short circuiting may 
ensue, and also to switch off the primary current before 
stopping the motor. 

The Mackenzie-Davidson Break is quieter. It consists 
of a large quantity of mercury in a box, into which at the 
surface, fans revolve on an axle from a motor inclined at an 
angle with the surface of the mercury. The same electrolyte 
is used as for the dipper. 

The Jet Interrupter is also a mercury break in which 
a jet of mercury strikes a metal tooth. Some are made 
where the mercury is pumped up by a centrifugal pump, 
the jet produced by the revolution of the pump, causing 
it to make contact with the tooth and on breaking, sets up 
a current. Others are made where the teeth revolve and 
the jets of mercury issue from the side of the containing 
vessel. The same electrolytes as for the others may be 
used. It is worked by means of an electro-motor or it can 
be worked by hand. It is a very satisfactory instrument, 



THE RONTGEN RAY APPARATUS 145 

the old objection of clogging of the jet holes being obviated. 
It can be used for currents of 20 amperes or more and up 
to 240 volts. 

The Sanax Interrupter is made on an entirely different 
principle from any of the others. In this a steel pear-shaped 
vessel is attached to the vertical axle of an electro-motor 
and contains a small quantity of mercury with paraffin as 
the electrolyte. Centrifugal force causes the mercury to rise 
up the sides of the bowl until it reaches a groove. Thus 
a ring of rotating mercury is formed. Inside the bowl on a 
vertical spindle placed eccentrically is a fiber disk with 2 
copper segments rotated by the mercury ring which makes 
and breaks the current. This form of break makes very 
little noise and has many advantages. 

The Auto-Magnetic is very efficient and gives little or 
no trouble. Briefly it consists of a vessel partly filled with 
mercury, and coal gas as an electrolyte. In this vessel is a 
horizontal axle fitted with blades which on revolving sweep 
in and out of the mercury. No motor is used but a series 
of field magnets, so that on switching on the current the 
blades revolve instantly, through the action of the field 
magnets. Unlike some others on the same principle it can 
be easily made to travel either very rapidly or slowly and 
also regulated to give from J milliampere in the secondary 
up to 25 milliamperes. 

The Electrolytic Interrupter consists of a large glass 
vessel partly filled with dilute sulphuric acid (sp. gr. 1200) 
into which dips a sheet of lead (cathode) and also a platinum 
wire (anode) fitted into a porcelain holder. The platinum 
emerges from a hole at the extremity of this holder about 
a quarter of an inch or so. On switching on, the current 
flows from the platinum point to the lead by reason of the 
conductivity of the electrolyte and in doing so bubbles of 
hydrogen form on the surface of the platinum thus break- 
ing the current but only for an exceedingly short time. The 
bubbles breaking off again, the current again flows when 
the same action takes place again. The advantage this break 
has over others is its rapidity and the great amount of cur- 
io 



146 THE X-RAYS OR RONTGEN RAYS 

rent that can be passed. One, two, or three anodes can be 
fitted either to work together, or as a single or double pole. 
The disadvantage of this break is the liability to reverse 
current which heats and spoils the t r-ray tube. Although it 
can work from any voltage from 50 to 250, yet probably 100 
volts is the best. It also makes much noise but this can be 
lessened by placing it in a sound-proof box, or attaching a 
rubber air cushion to the porcelain tube. 

Switchboard. — When two kinds of interrupters are 
used, as a mercury and electrolytic, a change-over switch 
is necessary and this is attached to the switchboard or 
table. The necessity arises from the fact that with a mer- 
cury break the condenser is used in the coil, but if an electro- 
lytic break is used, not only must the current be changed 
over it but also the condenser, not being used, must be 
u cut out." With this latter a large current may be put 
through the coil, and in the experience of the writer the 
best switch for satisfactorily breaking the current without 
any fusing of the contacts is the rapid switch made by 
Butt, which by one movement of the lever enables the 
operator to make an exceedingly rapid exposure or one as 
long as desired. 

Ammeters for measuring the current should be used, but 
voltmeters are not necessary. To measure the secondary 
currents milliammeters are necessary, as without one the 
amount of current passing through the tube is not known 
and the correct exposure a matter of guesswork. These 
are usually fitted with shunts, thus multiplying the reading 
of the index, because with a mercury break possibly only 
2 milliamperes may be passing, but when one of the modern 
mercury breaks, taking a large current, or the electrolytic, 
is used, as much as 20 to 30 milliamperes or more may be 
passed through the tube; a much higher reading is there- 
fore necessary. 

The Spinctermeter is the name given to the instrument 
formerly known as the spark gap, and consists of a pointed 
rod which can be pushed near to or drawn away from a 
ball or disk and measures the alternative spark gap. This 



THE RONTGEN RAY APPARATUS 147 

shows arbitrarily (for it varies according to the apparatus 
and amount of current passed) the resistance or penetrative 
power of the tube. 

The scientific and accurate measurement is obtained by the 
use of a radiometer, of which there are several. Benoist's 
consists of an aluminium disk graduated in steps, having 
in the centre a thin silver plate. This is viewed through 
the fluorescing screen, and when one of the aluminium 
steps has about the same transparency as the silver, the 
hardness or penetrative power of the tube is seen by the 
number of that step, so that a tube can be described as 
being of the hardness of, say, "No. 8 Benoist." 

X-ray Tubes. — These may be divided into three classes; 

1. Heavy anode. 

2. Light anode. 

3. Therapeutic. 

The first kind (H. A.) is for taking rapid exposures, and 
some of them are described as being extra heavy, while 
the L. A. is meant for currents of 2 or 3 milliamperes. But 
as a matter of fact these L. A. tubes will sometimes with- 
stand for a third- or a half -second 20 milliamperes, the 
writer having had experience of at least three L. A. tubes 
which gave several hundred such exposures. 

The third class, as their name implies, are solely for thera- 
peutic work, giving off abundance of rays but not having the 
cathode and anticathode adjusted for focus. 

X-ray tubes are made by several makers both in England 
and on the Continent, each maker having some special 
method of manufacture. 

Muller Tubes are made for long life and if strained too 
much, especially when new, the vacuum will get low. 
Automatic regulation devices are attached. 

In the Bauer Tube the chief feature is the valve for lower- 
ing the resistance. An infinitesimal quantity of air being 
admitted as desired. 

Some tube makers, as Cossors, attach to the tube an 
automatic device for lowering, whereby C0 2 , instead of air, 
is liberated into the tube. To keep the anticathode cool the 



148 THE X-RAYS OR RON T GEN RAYS 

rod holding it is prolonged to the outside and fitted with 
metal radiators so as to cool it by contact with the air. 

Another method is to have water in contact with the 
back of the anticathode, and another: copper tongs are 
inserted close to the anticathode and can be withdrawn 
and plunged into water to cool. 

The oscilloscope tube is employed to detect any trace 
of reverse current, and consists of a cylindrical exhausted 
glass tube about 8 inches long by 1| inches in diameter, 
containing 2 aluminium wires of equal length nearly touch- 
ing, with a disk of mica in the middle of the tube having a 
central hole. If the current is unidirectional a blue fluo- 
rescence is seen about the wire in one-half of the tube, but 
if any reverse is present the fluorescence is seen more or 
less on both wires, showing the amount of reverse current. 

DENTAL RADIOGRAPHY. 1 

The variety of uses to which the Rontgen ray has been put 
in the profession of dentistry has assumed such dimensions, 
especially since the outbreak of the war, that but little justice 
can be done to this all-important subject in the comparatively 
small space that can be devoted to it in this work. 

The question as to the intimate causal relation of many 
diseases of hitherto supposed obscure origin and foci of 
infection caused by pathological conditions of the apical 
regions of the teeth, has of late become such a vital one, and 
the aid afforded by dental radiography has been recognized 
as so essential, that an extensive work on this subject would 
represent a large volume, to say the least. 

For a more exhaustive study of this valuable addition 

3 By Dr. C. H. Abbot of Berlin. (In the revision of this chapter the 
writer has had to contend with the very serious disadvantage of being 
deprived, through the vicissitudes of war, of his own notes, films and other 
data. He has therefore been obliged to gather some of his material from 
various outside sources and is indebted to his colleagues for many hints and 
suggestions. Especial thanks are due to Drs. Ottolengui, H. F. Hamilton, 
A. I. Hadley, G. M. Brown and to Mr. J. J. Lowe for furnishing a number 
of films for illustration.) 



DENTAL RADIOGRAPHY 149 

to dental science the reader is therefore referred to those 
works which treat on that subject exclusively. Such works 
comprise, among many others, the Atlas by Prof. Dieck, 1 
a pamphlet by Port and Peckert, 2 works by H. R. Raper, 
Rollins, Williams, Pfahler, Tousey, Cieszynski, Price, Cryer, 
Sydney Lange, Van Woert, Rhein, McCoy, Shenton, Weski 
and many others. 

The writer hopes, however, by the following sketch of the 
various applications of this branch of electricity in dentistry, 
to incite the profession to its even more extensive adoption. 

This hope is indeed in a fair way of being realized since the 
publication of the first edition of this work; for what dentist 
would now consider himself "up-to-date" and abreast of the 
times who did not either own his x-ray outfit or who was not 
in touch with an x-ray specialist to whom he sends his patients 
for radiography. The most important factor of "checking 
up" his own work, makes the presence of an outfit in the 
dentist's office the more desirable, as, especially if in verify- 
ing his root-canal work, the making of several radiographs 
at short intervals should become necessary, the patient 
would naturally object to several visits to a specialist on the 
same day. In cases of a more complex nature, however, 
in which only the experienced specialist can produce a service- 
able radiograph, also in many cases requiring plates, or in 
case of doubt as to the reliability of his own film, the dentist 
can always refer the patient to a specialist for comparison. 

The properties and production of the rays are described 
elsewhere in this work. 

The following description of the appliances connected 
with the technic of dental radiography may provide some 
useful hints to the operator for obtaining the best results. 
One of the most important considerations is the determina- 
tion of the resistance or vacuum of the tube, and for this 
purpose a number of appliances have been devised, such as 

1 Archiv und Atlas der normalen und pathologischen Anatomie in typi- 
schen Rontgen Bildern. Anatomie und Pathologie der Zahne und Kiefer 
im Rontgenbilde. 

2 Ueber die Rontgenphotographie in der Zahnheilkunde. 



150 THE X-RAYS OR RONTGEN RAYS 

the Walter and Benoist scales, Wehnelt's cryptoradiometer, 
Beez's scale and Bauer's qualimeter, by means of which the 
resistance of different tubes can be gauged, given the same 
amperage and voltage of the current prior to its entering the 
tube. 

It is well to bear in mind that the more current is sent 
through the tube the harder or higher it will register on the 
scale, so that in determining its resistance, the same strength 
of current should always be taken as a base of calculation. 
Another means of determining the so-called hardness of a 
tube is to measure the length of the spark gap on the induction 
coil at the point where the spark can just jump the space 
between the two poles, and then to separate these poles far 
enough to prevent the current from doing so. This distance 
if determined beforehand — given a certain strength of current 
measured in milliamperes — will register the requisite resist- 
ance of the tube. 

If, for example, a tube is best adapted for certain dental 
uses, when " backing up" a spark of 7 inches at 5 milliamperes, 
it will be too hard if it backs up a spark of 8 inches and too 
soft if it does one of 6 inches. 

There are in the United States many excellent .T-ray 
outfits, and the dentist who wishes to equip himself will, 
by studying the various advertisements in the dental maga- 
zines, easily find something to meet all his requirements. 

Mention of the Coolidge tube, which has attracted so 
much attention among axray specialists, should not be 
omitted here. It does away entirely with the regenerating 
process necessary in all other tubes and has the further 
advantage of allowing the operator to control voltage and 
amperage irrespective of each other. 

The vacuum is estimated to be about 1000 times lower 
than in other tubes and remains constant. The anode and 
anticathode or target are identical and consist of a piece of 
tungsten attached to a rod of molybdenum; the cathode 
consists of a spiral of tungsten wire enclosed in a tube of 
molybdenum which projects slightly beyond the spiral and 
serves to focUs the electrons onto the target. The cathode 



DENTAL RADIOGRAPHY 151 

is heated either by a storage battery in connection with 
rheostat and amperemeter, or from the main current by a 
separate generator with ammeter, to control the amount of 
heat passing through the spiral and consequently the degree 
of penetration which is indicated by a secondary voltmeter. 
The amount of current is controlled by rheostat and indi- 
cated by milliammeter, The tube operates without fluores- 
cence and practically suppresses any current not flowing 
from anode to cathode, hence it does away with all rectifying 
devices. As will be gathered from the foregoing, this tube 
necessitates the installation of special apparatus which makes 
the preliminary cost considerable, but its life is claimed to be 
unlimited. 

The writer is not familiar with the English outfits, which 
are no doubt excellent, but respecting which he has no means 
of information at the present time. 

The human hand was at first most frequently used for 
the determination of the resistance of the tube, as it was 
very convenient and afforded a most reliable means for the 
purpose to the experienced operator. But the disastrous 
results of this method, which was long in use before the danger 
was realized, are now too well known to require further 
comment. "Skeleton" hands have been used in dark boxes 
with a fluorescent screen similar to the Wehnelt scale, and 
Dieck has devised a cryptoscope containing a section of the 
lower jaw with teeth, encased in wax so as to imitate approxi- 
mately the density of the surrounding soft tissues. These 
have proved very efficient in general use. 

The resistance most adapted to general dental work is 
about 6 to 6 1 on the Wehnelt crypt oradiometer (6 to 6J 
Wehnelt for short). One of the advantages of the Wehnelt 
is that there is no need for darkening the room, as the padded 
box can be pressed close to the eyes so that no disturbing- 
light is noticeable. It has one disadvantage, however, in 
that the subjective or personal element gives rise to dis- 
crepancies, as human eyes do not all see quite alike, and 
differences of impression of as much as 1 to 2 units have been 
registered by the same tube. The proper resistance of the 



15: 



THE X-RAYS OR RONTGEN RAYS 



tube depends upon the thickness and density of the object 
to be .r-rayed; for example, a radiograph of the whole skull 
would require a tube with the resistance of about 9 to 10 
Wehnelt. 

The writer has found the Bauer qualimeter used under the 
above-mentioned conditions a most reliable and satisfactory 
stand-by, for it does away with the more or less difficult 
comparison of shades, and registers the condition of the tube 
in plain numbers. This, as well as all other methods, how- 
ever, has a slight drawback, inasmuch as it takes some few 
seconds for the indicator to cease oscillating and to point 
to the number in question, thus permitting the tube to grow 
a trifle " harder" by virtue of its longer use, but with a little 
experience, the observer will be able to anticipate the 
eventual point of rest. 

The following table compares the principal scales: 



Bauer . 


1.0 


2.0 


3.0 


4.0 


5.0 


6.0 


7.0 


8.0 


9.0 


10 


Wehnelt . . 


1.5 


3.0 


4.5 


6.0 


7.5 


9.0 


10.5 


12.0 


13.5 


15 


Walter . . 


1.0 


1-2 


2-3 


3-4 


4-5 


5-6 


6-7 


7-8 






Benoist 


1.0 


2.0 


3.0 


4.0 


5.0 


6.0 


7.0 


8.0 


9.0 


10 



When the operator is in a position to direct the rays in a 
straight line through the middle of the cylinder with the aid 
of the centralizing telescope or "pointer" the next question 
he must consider is the relation of this line: (1) to the axis 
of the tooth or root, and (2) to the plane of the film or plate; 
and here he must observe certain principles of projection 
which in themselves are simple, but which it may be well to 
recall. 

The first is the consideration of the relative distances 
between the target, the object to be .r-rayed and the film 
or plate, and the effect of these upon the size of the skia- 
graph compared to the object itself. This may be easily 
illustrated by the accompanying diagrams, and roughly 
stated by the following self-evident rule. 

T being the target, cd and Cidi the object to be .r-rayed, 



DEXTAL RADIOGRAPHY 



153 



and p the film or plate, the nearer the object cd is to the plate, 
the smaller the image ah will be, and the farther from the 
plate, the larger the image c^di will be on the plate (iib x \ the 
distance from T to the plate remaining the same, the image 
of the object will be larger, the nearer the target is to the 
plate; ab produced by the rays starting at T is longer than 
aj>i with the target at T x . 




The distance between the target and the plate or film in 
dental radiographs should usually be about 35 cm. with the 
film pressed as closely to the alveolus as possible. In tak- 
ing radiographs of the teeth of the upper jaw, with the plate 
or film held between the teeth and taken from above, the 
distance should not be less than 35 to 40 cm. 

The direction of the rays in their relation to the axis of the 
roots (especially in the upper teeth) and the plane of the film 
is of great importance in producing an approximately correct 
image of the tooth or root on the film, and here the rules 
advocated by Cieszynski and Dieck should be observed as 
closely as possible, provided there are no other conditions, 
such as can only be brought out by a distorted picture; this, 
however, will be referred to later. 



154 THE X-RAYS OR RONTGEN RAYS 

The rule to be^observed is to direct & the rays vertically 
through the apex of the root in question onto an imaginary 




^oiS^ 



tn 



Imaginary Dividing 



Line 



Fig. 66 




Fig. 67 



line dividing the angle formed by the axis of the root and the 
plane of the film. This is shown in Fig. 66. 



DENTAL RADIOGRAPHY 



155 



in Fig 



An instrument devised by Dieck for this purpose is shown 
67. 

The more the rays are directed from above, the more fore- 
shortening of the tooth will occur, and the more from below, 
the more elongated the teeth will appear on the film. 

Occasionally it may be important to procure an exact 
measurement of the length of a root, which can easily be 
ascertained provided the operator can insert a broach of a 
given length into a part of the canal before exposure. This 
can be calculated by the following proportion: 

If the length of our broach ab is known we can measure on 
the radiograph the length of the image of the root a'c' ', also 
of the broach a'b'. The actual length of the root to be calcu- 
lated being x we have the proportion: 



a'b' : ab = a'c' : x 




ab X a'c' 
X - a'b' 




or, for example, if ab = 6 mm. 




a'b' = S mm. 




a'c' = 10 mm. 




we have 8:6 = 10 : x 




6 X 10 
and x = — = 


7.5 mm 




Fig. 6S 



For determining the length of the roots of vital teeth or 
those that cannot be entered by a wire, Ottolengui has de- 
vised a clever means of measurement. It consists in winding 
a wire around the neck of the tooth in question, allowing one 
end to extend to the occlusal or incisive surface, and the other 
outside the gum as nearly as possible in the direction of the 
axis of the root. By taking a radiograph with the wire applied 



156 



THE X-RAYS OR RON T GEN RAYS 



in this way and measuring on the film the length of the tooth 
in relation to the wire attachment, and this again to its 
actual length, a fairly accurate measure of the root from the 
horizontal portion of the wire to the apex can be obtained. 
See Fig. 69 and equation. 




or for example : 



ab = 15 mm 
a'b' = 16 mm 
b'c' =18 mm 



_ 15 X IS 
16 
17.8 mm. 



Fig. 69 



This of course will not be quite correct in case of a labio- 
palatal or lingual curvature of the root. 

One of Dr. Ottolengui's colleagues having expressed a 
doubt of the accuracy of this method, on account of the 
distortion produced by taking pictures at various angles, 





Fig. 70 



Fig. 71 



Dr. Ottolengui decided this matter as follows: Taking a 
dried skull, he placed a wire around the tooth neck at exactly 
one inch from the apex and then took the pictures at extreme 
opposite angles. The illustrations show the resulting radio- 
graphs. Computed by one of these, the tooth was shown to 



DENTAL RADIOGRAPHY 157 

be y"o1t i ncn m length and computed by the other, it was 
shown to be y 9 ^- inch in length. In each instance, therefore, 
the variation from the truth was y-j-g- inch. As the knowl- 
edge of the length of a living root is usually required only to 
determine whether there is enough root to carry a crown or 
bridge abutment, it is seen that this method is sufficiently 
accurate. 

In taking arrays of teeth in the lower jaw the placing of the 
film is comparatively simple for the incisors, bicuspids, and 
molars; for the canines, owing to their occupying a more or 
less "corner" position in the arch, the holding of the film is 
not always a simple matter, for unless it is very narrow it 
will bend a great deal, causing considerable distortion, espe- 
cially of the adjoining teeth. In cases where it is desirable 
to include the apex of the roots and the parts underlying 
them, especially in lower wisdom teeth, the operator often 
encounters a good deal of opposition on the part of the 
patient, on account of the irritation to the soft tissues caused 
by the wrapping of the film. A film-holder which obviates 
this difficulty is described in another part of this chapter. 

In cases where the formation of the lower jaw is such that 
it is difficult or impossible to obtain a view of the apex, or 
parts underlying it (as for example an abscess cavity or cyst) 
without distortion, it will be well to direct the rays consider- 
ably from below in order to include these portions, although 
this will produce a somewhat distorted image. But where 
it is a matter of locating an abscess-cavity or cyst, this is 
of no consequence compared to the establishment of the point 
in question. (Fig. 72.) 

The interpretation of the film or plate is naturally fully as 
important as its production, and it should be kept in mind 
that what is seen is the effect of the difference of absorption 
which the rays undergo in their passage through the tissues 
which they penetrate. This again depends on the density 
and thickness of the object, or the combined densities and 
thicknesses of superimposed layers of different structures 
such as roots, bone, pus, filling materials, etc. For instance, 
the overlapping part of a buccal molar root over part of a 



158 



THE X-RAYS OR RON T GEN RAYS 



palatal one, might give to the unobserving a misleading pic- 
ture, when proper reasoning will put the operator right. The 
designation "positive" and "negative" in works on the Ront- 
gen ray is often a little confusing. In most text-books the 
illustrations consist of prints of the films, while in practice 
the operator generally uses the original film itself. On the 
latter the teeth and bones show light, and the softer tissues 
and cavities appear dark, as they offer the least resistance 
to the passage of the rays; on the former, of course, the 
reverse is the case, and as the prints or positives are generally 
used as illustrations in the text-books, the respective shadows 
will be referred to as they appear in these positives, unless 
otherwise expressly designated. 




■<mc 




Fig. 72 

Ottolengui has very logically suggested the standardization 
of the terms: 

(a) Radiopaque (radiopacity) from "radius" a ray, and 
"opacus," impervious to light, 

(b) Radiolucent (radiolucency) , 

(c) Radioparent (radioparency), 

which two last expressions bear the same relation to each 
other as "translucent" and "transparent" and are readily 
intelligible. 1 

This would do away more or less with the term "rarefied" 
in the reading of radiographs which is often misleading and 



1 See Dental Items of Interest, February, 1917, p. 141. 



DENTAL RADIOGRAPHY 159 

denotes rather a pathological condition, whereas the word 
" radiolucent" is simply the statement of a physical condition, 
which may or may not imply a diseased bone area. It may 
be caused by the presence of a foramen or by apiectomy (or 
root amputation). The term "Radiodontia" suggested by 
Raper commends itself to the writer as terse and compre- 
hensive. 




In the interpretation of radiographs there are several 
anatomical points to be recalled, the neglect of which 
might at times be the cause of a misleading diagnosis. One 
source of error may be a small dark spot on the film caused 
by the anterior palatine foramen, which may be mistaken 
for destruction of bone resulting from abscess. The mental 
foramen also may give rise to the same faulty diagnosis, 
although more rarely, owing to its lower position in the 
inferior maxilla. The canal of the inferior dental nerve may 
also be mistaken for a diseased condition of the bone. 

The suspicion that molar or bicuspid roots may be pro- 
jecting into the antrum is also often suggested to the operator 
by the appearance of the film, and a correct diagnosis may be 
very difficult without accurate observation and reasoning. 
If the topography of the antrum is considered in its relation 



160 THE X-RAYS OR RONTGEN RAYS 

to the roots of the molars and bicuspids and the hard palate, 
it will be easily understood that owing to the slanting direc- 
tion of the rays from above downward, one or more roots of 
the above-named teeth are often projected into the image 
of the antrum. Of the molars this is most frequently the 
case with the palatal root (Fig. 73). The question of per- 
foration of the floor of the antrum by a diseased root requires 
a very sharp radiograph, marking the contrasts very clearly 
and showing whether the pericementum and periosteum of 
the alveolus are intact or not. The walls of the alveolus 
will show as a thin white line (linea dura or alba) on the film, 
and the space occupied by the pericementum as a dark line. 
In any case presenting the least doubt two or more radio- 
graphs from different directions or stereoradiographs should 
be taken. Portions of the antrum itself may be mistaken for 
a diseased condition of the maxilla, a granuloma or cyst. 
There may also be a confusion of the lower symphysis of the 
malar bone and a wall of the antrum in the reading of radio- 
graphs. When using a rather soft tube the nares may also 
be mistaken for "rarefied" areas of bone, a point to be con- 
sidered. In every case when interpreting a film we should 
not only consider the immediate area under suspicion but 
compare the appearance of the bony tissues at that place with 
all the surrounding structures of the other teeth and roots on 
the film. 

For viewing radiographs a number of illuminating boxes 
containing two or more lamps have been put on the market 
which enable the operator to examine the films by different 
degrees of light by varying the number of lamps or regulating 
the current by a rheostat, for different parts of the same film 
may not show to equal advantage under the same light 
conditions. Generally it is best to view the film against 
ground glass or opaque celluloid. On dull days a light gray 
sky may also serve as a good background. 

The question as to which one of two (or more) teeth or 
roots partly lying in the line of the rays is before or behind the 
other, is one which may also arise in practice. This may not 
be an easy matter to decide without the aid of stereo- 



DENTAL RADIOGRAPHY 161 

scopic radiographs, but the tooth which appears relatively the 
smallest and most sharply outlined will obviously be the one 
nearest the film and consequently nearest the palate in the 
superior maxilla, or if they are lower teeth, nearest the lingual 
wall of the mandible. 

The proper time of exposure is of the utmost importance 
in obtaining satisfactory results in x-ray work. Here again 
it is very difficult to advise the beginner, as so much depends 
upon the strength of the primary current, the size of the 
induction coil or whatever apparatus the operator is using. 

With a coil furnishing a 40 to 50 cm. spark, and a primary 
current of 25 to 35 amperes and a tube of approximately 
5 or 6 Wehnelt (units) the operator should under ordinary 
conditions obtain excellent results with an exposure of from 
six to eight seconds, unless the bone is exceptionally dense, 
when a somewhat longer exposure should be made. The 
time for taking the lower molars (especially second and third) 
should be about double that for the front teeth, owing to the 
greater thickness of the bone to be penetrated. Practice 
will be the best teacher in this respect. Less powerful out- 
fits will necessitate relatively longer exposures. 

For those who can afford interrupterless or the Coolidge 
tube outfits, the time of exposure is of course proportionately 
shorter and in many cases may be cut down to a second or 
even a fraction thereof, but generally a little longer exposure 
with correspondingly less strength of current will give more 
satisfactory results. For nervous patients or children, or in 
cases where the insertion of the film at the back of the mouth 
is liable to cause choking or nausea, the possibility of cutting 
down the exposures to that extent is a distinct advantage 
which can be readily understood. 

The operator working with a more modest outfit has also 
a means of abbreviating his exposures, viz., by using the 
so-called intensifying screens with his films. This screen 
consists of card-board covered on one side with a preparation 
containing principally tungsten or wolfram which fluoresces 
and absorbs the x-rays to a marked degree, acting on the 
film or plate for some time after the exposure; it is therefore 
11 



162 THE X-RAYS OR RONTGEN RAYS 

undesirable to leave the plate packed with the screen long, 
for fear of causing overexposure. One drawback with these 
intensifiers is that they are liable to fog the radiograph to 
some extent and that they do not keep very long without 
losing some of their strength. Still, when we consider that 
they are capable of reducing the time of exposure at least 
tenfold, we cannot but acknowledge that they certainly 
should have their place in every outfit. The screen is best 
applied by packing it with its glossy side facing the sensitized 
side of the film. 

The intensifying screens are of especial value in the taking 
of glass-plate radiographs, involving the whole or parts of the 
skull, as the longer exposures will of course raise the resist- 
ance of the tube to a considerable extent, a factor which is 
particularly undesirable in stereoscopic work, for the regen- 
eration of the tube between the first and second exposures 
should be avoided for obvious reasons. 

Stereoscopy in Dental X-ray Work. — It is easily understood 
that x-ray stereoscopy differs from ordinary stereoscopy, 
inasmuch as the exposures are made consecutively with the 
same tube, which is moved a certain distance from either 
side of the position from which the simple x-ray would be 
taken. The plane, of course, must be the same and the film 
or plate must be placed in the same position for the second 
that it occupies during the first exposure. A stereoscopic 
tube with two cathodes and anticathodes, the focal centres 
of which are placed 5 to 6 cm. apart, has been devised by 
Fiirstenau, but this seems hardly necessary when the oper- 
ator has a stand equipped with a graduated scale upon the 
horizontal arm. 

In this connection it will be well to bear in mind that 
stereoscopy is not to be depended upon for furnishing abso- 
lutely correct relations of the different parts. This conclusion 
is amplified by the fact that there is so much diversity of 
opinion among different authorities as to the proper distance 
to which the tube should be moved away from the median 
line for the two exposures. The distance should approximate 
that of the eyes from each other. Some say that this should 



DEXTAL RADIOGRAPHY 163 

be 6, others advise 7 cm. Marie and Ribault have published 
a table giving a number of different figures 1 varying from 
2 cm. to 10 or even 16 cm. for the displacement of the tube 
in .r-ray stereography, according to the distance of the part 
in question from the anticathode, and the thickness of the 
object. This does not appear very rational, as the distance 
separating the human eyes does not vary to such an 
extent. Albers-Schonberg, 2 as well as Kells, 3 in their works 
describe a complicated apparatus, giving to the tube not 
only a lateral but a rotary displacement for the most powerful 
rays to pass through the object to be stereographed. But 
this seems to the writer unnecessary, as the rays spread fan- 
like from the target, and those striking the object, although 
not the most central ones, still are strong enough to produce 
excellent results. 

Nevertheless the stands for stereoscopic work are to be 
recommended to those who can afford the expense, especially 
where larger areas are to be taken. The rotary (or converg- 
ing 4 ) movement of the focussing cylinder allows the whole 
area to appear on both pictures, whereas by moving the tube 
laterally a part of each image which is circumscribed by the 
preliminary focussing upon the principal point of interest 
would become obliterated by the corresponding wall of the 
cylinder. This may in a measure be compensated by the use 
of a cylinder of larger diameter, which, of course, admits a 
greater number of secondary rays. 

These diagrams will show that in Fig. 74 only the middle 
part of the object will appear on both exposures, whereas in 
Fig. 75 the whole object appears in stereoscopic projection 
by either of the two methods employed. In the case of Fig. 
74 the whole object nevertheless appears in the stereoscope; 
only the middle part, however, is really plastic. 

For stereoscopic radiography with plates, sliding plate 
holders have been put on the market enabling the inter- 

1 Archives d'Eleetricite medicale, July 15, 1899. 

2 Die Rontgentechnik. 

3 Dental Cosmos, July, 1912. 

4 Kelly-Koett stand used by Ivy, of Milwaukee, see Cosmos, July, 1917. 



164 



THE X-RAYS OR RONTGEN RAYS 



change of plates without disturbing the position of the 
patient. Both plates are placed in the holder simultane- 
ously, the one being covered by a sheet of heavy metal 
during the exposure of the other. Both plates should be 
developed together for the same length of time in order to 
produce the most uniform appearance. 




Fig. 74. — Lateral move- 
ment of tube (cylinders par- 
allel) . b, body to be x-rayed ; 
p, photographic plate; t t', 
target; c c', cylinder; cr, cr', 
central rays. 



Fig. 75. — 1, rotary movement of tube 
(cylinders converging) ; 2, lateral move- 
ment of tube (cylinders converging). 



The distance from target to film or plate should not be less 
than 35 cm.; for the whole head it should be at least 50 cm. 

The plates can be viewed in the Wheatstone Stereoscope, 
in their natural size, or after reducing, in any hand stereo- 
scope. Various ingenious devices for localizing foreign bodies 
in the head and body have been invented in connection 
with stereoradiography, which have proved of inestimable 



DENTAL RADIOGRAPHY 165 

value during this war, in cases of gunshot wounds, for deter- 
mining the position of bullets and fragments of shells, etc. 

A few years ago there was considerable discussion about the 
feasibility of examining the teeth with a fluorescent screen, 
or taking radiographs with the anticathode of a tube of 
suitable dimensions and construction inside the mouth. 
Tousey tried these tubes, also Guye, of Geneva, and Bauer, 
of Berlin, but these methods were soon abandoned on account 
of the very considerable danger to the patient. The idea of 
simply placing a little tube in the patient's mouth, holding 
the plate wherever desired and turning on the current, is very 
alluring, but other considerations make it appear less so, 
especially the prospect of the patient sustaining severe burns 
for which the operator is responsible. 

Extra-oral exposures in which the film or plate is held out- 
side of the mouth, often become necessary when larger por- 
tions of the maxilla or other bones of the head are involved. 
Here the operator will do well to refresh his memory in 
regard to the topographical anatomy of the head and neck, 
as the overshadowing of the parts to be examined by various 
other portions of bone may give rise to many errors in 
diagnosis. 

In taking extra-oral radiographs of the teeth, the parts 
especially desired to be brought out should rest as near the 
plate as possible. Care should be taken to avoid the projec- 
tion of the styloid process to confuse the image. For bicus- 
pids and molars the rays should be directed to pass between 
the ascending ramus of the mandible and the vertebral 
column. The mouth should be closed and the head tilted so 
as to avoid bringing the opposite side of the mandible onto 
the picture. For the front teeth the rays should be directed 
from behind, the patient leaning well forward. Experience 
and a knowledge of topographical osteology of the head will 
be the best teacher in this by no means simple technic. 

It is rarely possible to obtain a large radiograph of this 
kind without distortion of some part or other, but that does 
not necessarily make it any less valuable, as in most cases the 
necessarv allowances can be made to arrive at correct con- 



166 THE X-RAYS OR RONTGEN RAYS 

elusions; but where it is possible to avoid such a condition 
it is preferable to do so. For this purpose a "phantom" 
skull attached to a stand has been devised by Dieck, which 
is placed so that the centralizing telescope of the protective 
box containing the tube may be occupied by the patient's 
head during the exposure. 

The tedious process of cutting and wrapping the films 
has been superseded by the manufacture of ready-packed 
x-ray films of various sizes, rapid and slow, and obtainable 
through most dental firms. A number of ingenious devices 
have been thought out for holding the film in place in 
the mouth. Among others, a hardened Stents impres- 
sion, trimmed to suit the needs of the case, has been recom- 
mended. Cieszynski has constructed film-holders for the 
upper and lower jaw, the upper one consisting of a metal 
frame to be held in position by the bite of the patient, 
aided by the use of a rubber bag to be inflated after the film 
has been inserted. The writer, however, considers that up 
to the present nothing surpasses the human finger as a film- 
holder for general use, and were it not for a certain danger 
to the operator or the assistant who lends his hand to this 
purpose, this simple method would be the best. 

Ottolengui recommends the use of a rubber dam clamp 
for holding films in the mouth, a suggestion that commends 
itself especially where the radiopacity caused by the clamp 
does not collide with the object in view, as would be the case 
with pulp stones. 

Danger of X-ray to Patient and Operator. — As regards the 
patient, the danger of x-rays can be very readily dismissed 
from the mind so far as radiographs are concerned, for the 
exposures, even the longer ones, are now too short to do 
even a child the least harm, unless the operator is guilty of 
the grossest negligence. It is nevertheless desirable, espe- 
cially in the interest of the operator, to observe a few pre- 
cautions so as to avoid being held responsible, even for 
imaginary burns or skin troubles due to other causes. It is 
well to introduce a cowhide or an aluminium filter, the latter 
of 2 mm. between the tube and the patient's face, as the soft 



DEXTAL RADIOGRAPHY 167 

or superficial rays that are the principal cause of injuries to 
the skin, are absorbed without impairing the clearness of the 
radiograph. In the case of an accusation on the part of an 
imaginative patient, the proof that the operator used these pre- 
cautions would help to exonerate him in the eyes of the law. 
A rubber cloth or apron laid about the patient's shoulders 
would also act as an insulator for sparks or effluvia emanat- 
ing from the wires or metallic parts of the tube that might 
cause an unpleasant shock to the patient without probably 
doing him any harm. The more even the semblance of 
carelessness can be avoided, the greater will be the patient's 
confidence and appreciation. To "make assurance doubly 
sure" an insulated grounding wire or chain should connect 
the metallic parts of the stand that come in contact with the 
tube to a gas or water pipe in the office. 

The danger, however, is immeasurably more serious in the 
case of those who occupy themselves with this work exten- 
sively. It has been stated before that the hand should never 
be used as a means of testing the tube, and the bare fingers 
only in the rarest and most urgent cases, where a protective 
glove is too bulky. This glove should form part of every 
dental x-ray outfit, and can be purchased at the regular 
x-ray supply stores. These gloves are made of a protective 
material consisting of thick rubber cloth impregnated with 
metal, and are well-nigh absolutely impervious to the rays. 
A compromise between a glove and a mitten has been used 
in the writer's surgery for some years and has given much 
satisfaction. It consists of a thumb and forefinger, and a 
casing for the other three fingers together; it is somewhat 
clumsy, but serves to hold the film well in place when once the 
same has been properly inserted without the glove, which 
can be slipped on while the film is temporarily held with the 
other hand. Tousey mentions another way to make pro- 
tective gloves : Soak thick leather gloves in a saturated solu- 
tion of bismuth chloride, then immerse in cold running water 
for an hour; repeat three or four times. This method is 
published by Dr. William Mitchell. Archives of the Rontgen 
Rays, April, 190S. It goes without saying that the same 



168 THE X-RAYS OR RON T GEN RAYS 

precautions used by the .T-ray operator for his own pro- 
tection should be employed for his assistant, and in all 
cases where the him can be held by the patient himself or by 
artificial means, both operator and assistant should disappear 
behind a good-sized lead-glass screen during the time of 
exposure. 

The question of secondary rays is one of such importance 
that it must be touched upon here, for not only do these 
rays expose the operator to a certain amount of danger but 
they impair the clearness of the radiograph. 

The impact of the primary Rontgen rays upon any solid 
or liquid body gives rise to rays which are called secondary; 
they radiate in all directions from the point of impact and 
act similarly to reflected rays; consequently they may to 
some extent be dangerous to those exposed to them, although 
they are not as powerful as the primary rays and possess 
certain properties that differ from them. 

The other disadvantage of these secondary rays is their effect 
upon the sharpness of the image on the plate. They arise 
from contact with the wall of the tube and are more or less cut 
out by the lead cylinder attached to the stand (Fig. 76), but 
this does not do away with the secondary rays originating in 
the body itself which is to be a>rayed, for these are beyond 
the pale of the cylinder, and their effect could only be elimi- 
nated by interposing another cylinder of suitable dimensions 
between the object and the sensitive plate (Fig. 77). But 
such a one, with a diameter large enough to include all of 
the desired image, would have to be too long to be practicable; 
in other words, it would remove the body too far from the 
plate. Dr. G. Bucky, of Berlin, does away with this necessity 
in a most ingenious w T ay. He reasoned that the smaller the 
diameter of the cylinder the nearer the object could be 
approached to the plate, so he constructed a series of small 
compartments of only 1 or 2 cm. in length with correspond- 
ingly small diameters, and walls converging toward the focal 
centre of the tube. The results are most remarkable. The 
image on the plate by this method is divided by a grille or 
net-work of many fine lines, but this can hardly be called a 



DENTAL RADIOGRAPHY 169 

drawback compared to the increased clearness of the image, 
and in many cases it may even be deemed an advantage, 
as it furnishes a scale of measurement that may be very 
desirable. Its use for dental work is restricted to those cases 
where a plate of some size is desired, such as for diagnosis of 
troubles of the antrum or frontal sinus; in these cases it 
should prove valuable. 





Fig. 76 Fig. 77 

Figs. 76 and 77. — Dotted lines indicate secondary rays. 

The appearance of the grille on the plate can now, as the 
writer is informed, be avoided by an improvement upon 
the first idea, also by Dr. Bucky, consisting of an arrange- 
ment by which the whole grille is moved during the exposure 
so that all parts of the object to be .r-rayed will be equally 
subjected to the penetration of the rays. This lengthens 
the exposure only by a very short time, but cuts out the 
secondary rays to the same extent as if stationary. This 
new apparatus bids fair to attract universal attention after 
the war. 



170 THE X-RAYS OR RONTGEN RAYS 

THE USES OF THE X-RAYS IN DENTISTRY. 

Under various headings the uses to which the x-rays are 
put in dentistry are as follows: 

A. For purposes of diagnosis. 

B. For "checking up" the work of the operator. 
A. Diagnosis. — 

I. For the detection and location of unerupted or 
impacted teeth in the practice of orthodontia and 
in pathological conditions brought about by the 
same. 
For the determination of: 
II. The amount of absorption of roots or bone. 

III. The destruction of bone as a result of alveolar abscess 

and granuloma. 

IV. The presence of cysts. 

V. The destruction of the alveolus in pyorrhea. 
VI. The position of broken-off nerve broaches or other 
instruments, as well as perforations. 
VII. Fractures of roots. 
VIII. The existence of pulp stones or deposits of bone in the 
pulp chamber. 
IX. Caries of roots under crowns or caps and approximal 
cavities in teeth which closely approximate. 
X. Antrum troubles (roots extending into, or foreign 

bodies in antrum). 
XL Neuralgia (exostosis and hypertrophy). 
XII. Necrosis (sequestra). 

XIII. Tumors. 

XIV. Fractures of jaws (gunshot lesions). 

XV. Foreign bodies in the esophagus, larynx or bronchi, 
resulting from accidents during dental operations. 
B. For "Checking Up" the Work of the Operator. — In the 
determination of: 

I. The length, shape and direction of roots. 

(a) For crown and bridge-work. 

(b) For extraction (especially of the lower wisdom 

teeth). 



THE USES OF THE X-RAYS IN DENTISTRY 171 

II. The thoroughness or lack of thoroughness of root 
canal fillings. 

III. For "checking up" the different stages of root canal 

treatment and 

IV. For the same purpose in apiectomy. 

V. For determining whether an inlay or other filling 
projects beneath the gum. 

A. 

I. In recent years, through the influence of Angle and 
others, the regulation of the child's teeth is undertaken much 
earlier than when the old maxim obtained of waiting till 
all the permanent teeth had erupted. The diagnosis of the 
position or possible non-existence of teeth in the maxillae of 
young subjects is of vital importance to the orthodontist. 
The .T-ray is of inestimable value in these cases as a means, 
and in most cases as the only means, of accurately deter- 
mining the existing conditions, and it is not an exaggeration 
to say that without it in many cases treatment would better 
be postponed until the eruption of the permanent teeth. 

In the case of impacted posterior teeth an extra-oral 
radiograph is often indicated and should there be any doubt 
as to the relative position of the roots of erupted and those 
of impacted teeth, a stereoscopic skiagraph is often of great 
value. 

Radiography is also useful in determining the size and 
length of the roots of teeth to be moved. Should these teeth 
remain permanently loose after regulating, the operator 
would certainly be held responsible unless he had taken 
radiographs before the beginning of the treatment. 

In the event of the loosening of teeth with strong and long 
roots the orthodontist stands a far better chance of exonera- 
tion than had this precaution not been taken; whereas if 
permanent loosening takes place when the roots are small and 
short, the dentist would in every case be blamed and held 
responsible for having failed to avail himself of this sure 
method of determination previous to beginning treatment. 



172 



THE X-RAYS OR RONTGEN RAYS 



In cases of impacted teeth the determination of the angle 
of axial deviation from the proper direction, which prevents 
the eruption, can be very accurately obtained by means of a 
radiograph. Occasionally more than one view will become 
necessary, with a different direction of rays. A few cases 





Fig. 78 



Fig. 79 



have occurred in the writer's practice where the simple separa- 
tion of the two teeth adjoining a slightly impacted one, has 
afforded space enough for the latter to erupt easily. 

Fig. 78 shows an impacted left lower second bicuspid with 
deciduous second molar. After extraction of the latter and 




Fig. 80. — Stereograph of right upper canine. 

separation of the first molar and first bicuspid the tooth 
assumed its normal position (Fig. 79). Fig. 80 shows an 
impacted right upper canine, the position of which appears 
clearer in the stereograph than in the single film. After 
widening the arch and separating the lateral incisor and 



THE USES OF THE X-RAYS IN DENTISTRY 173 

first bicuspid, the canine should be able to erupt normally. 
Radiographs taken at various stages during the process of 
separating the two teeth adjoining the impacted one are very 
desirable in determining the necessary force to be applied. 




Fig. 81. — Impacted canine. 

Figs. 81 and 82 show impacted upper canine. 

Cases in which the radiograph has shown the hopeless 
condition of missing incisors and canines are unfortunately 
not rare. 





Fig. 82. — Impacted canine. Taken 
by J. J. Lowe, Boston. 



Fig. 83. — Impacted canine in 
seemingly otherwise edentulous 
maxilla. Taken by J. J. Lowe, 
Boston. 



Fig. 84 shows a condition of two missing laterals which 
relegates the case from the orthodontist to the mechanical 
dentist. 



174 



THE X-RAYS OR RON T GEN RAYS 



Impacted teeth are the cause of many pathological con- 
ditions by virtue of the abnormal pressure they exert upon 
the roots of teeth and various nerves and other tissues. 




Fig. 84. — A case of missing tooth germs. 





Fig. 85 
Figs. 85 and 86. — Impacted lower wisdom teeth. 

Boston. 



Fig. 86 

Taken by J. J. Lowe, 



Absorption of the roots of neighboring teeth and caries of the 
same is no rare occurrence and could not be determined with 
any certainty by clinical diagnosis alone. The .r-ray is an 
indispensable means of ascertaining the truth in these cases. 



THE USES OF THE X-RAYS IN DENTISTRY 175 

In cases of inflammation of the tissues surrounding an 
impacted lower wisdom tooth which presents a condition 
simulating ankylosis, and making extraction necessary, the 
shape and position of the roots of the teeth may become of 
vital importance, and here again the x-ray is of inestimable 
value, and no up-to-date dentist would care to undertake such 
extractions without obtaining a radiograph as a guide in 
operating. 

In cases in which the operator sees a possibility of such 
a condition in his patient's mouth, it is advisable to have a 
radiograph taken while the condition still permits of the 
mouth being opened and the film inserted comparatively 
easily, which in the case of the lower wisdom teeth is a 



Fig. 87.— Film holder. 

proceeding accompanied by considerable discomfort to the 
patient even under normal conditions. For this reason, and 
especially in inflamed conditions of the angle of the jaws, 
Heinz Bauer has constructed a film holder which the writer 
has found indispensable at such times. The film holder 
consists of a German-silver case of suitable size, attached to 
a movable handle. After inserting the film the case is closed 
by an aluminium shutter which is easily penetrated by the 
rays, offering hardly more resistance than the paper packing. 
It can be readily sterilized, and forms a most important part 
of the dental .r-ray operator's outfit. 

Tousey speaks of a film holder that is somewhat similar 
in shape, but the ease with which Bauer's may be adjusted 



176 



THE X-RAYS OR RONTGEN RAYS 



to fit either side of the mouth seems to the writer a great 
advantage. 

II. Many cases of absorption of the apical part of roots 
have (before Rontgen's discovery) proved to be one of the 
greatest disappointments to the dentist. Many hours of 
treatment, a burden to the dentist and vexation to the 
patient, might have been spared to both had the operator 
been able, as he is now, to see if such treatment is hopeless or 
not. The writer has in mind a case which, instead of requir- 
ing six months of ineffectual treatment with the broach 
would have been completed in one sitting with the forceps 
had x-rays been available. Even minute degrees of absorp- 
tion may be the cause of never-healing fistulse and can easily 
be recognized on a good, sharp radiograph, and the tooth 
condemned to extraction or root amputation without further 
useless treatment. 





Fig. 88 



Fig. 89 



Figs. 88 and 89. Cases of absorption in connection with 
alveolar abscess. 

Fig. 90 shows left upper first and second bicuspids taken 
six years after amputation of roots. Both teeth firm and 
surrounding tissues healthy. 

Fig. 91. Case of fistula of right upper central incisor, 
carrying a pivot tooth, and accompanied by extensive loss 
of bone structure. Amputation of apex was resorted to. 
Fig. 92 shows end of root lost in abscess cavity during opera- 



THE USES OF THE X-RAYS IN DEXTISTRY 177 

tion. Fig. 93 shows condition after amputation. Fig. 94. 
Case a year and a half after operation. The cavity has been 
almost entirely replaced by newly formed bone. 





Fig. 90 



Fig. 91 





Fig. 92 



Fig. 93 





Fig. 94 



Fig. 95 



12 



178 



THE X-RAYS OR RONTGEN RAYS 



Fig. 95. Left upper first molar four years after amputation, 
of anterior buccal root; tooth firm and is doing good service. 




Fig. 96 

The radiograph is also of use in cases of pulp exposure in 
deciduous teeth in which it is desirable to apply arsenic. The 
degree of absorption of the roots shown on the film will help 
to decide the operator as to the safety of the procedure. 




Fig. 97. — Deciduous lateral with 
partly absorbed root and missing 
'permanent lateral incisor. Taken 
by J. J. Lowe, Boston. 




Fig. 98. — Absorption of roots of 
lower deciduous molar without under- 
lying permanent tooth. Negative. 
Taken by J. J. Lowe, Boston. 



The old theory that the roots of the deciduous teeth are 
absorbed, owing to the pressure upon them by the erupting 
permanent teeth, has been conclusively disproved by radi- 
ography. For many arrays have shown the roots of deciduous 
teeth to be partly or wholly absorbed without a trace of a 



THE USES OF THE X-RAYS IN DENTISTRY 179 

permanent tooth under them to which this absorption could 
be attributed. 

Fig. 96 represents the left upper deciduous second molar 
with roots nearly wholly absorbed without any trace of a 
bicuspid above it. 

When teeth have been broken off as a result of an accident, 
the x-ray is also a very valuable way to determine the stage 
of development of the root prior to devitalizing or crowning. 

Ill and IV. The x-ray has proved itself to be of inestimable 
value in the diagnosis of the extent of destruction of bone as a 
result of alveolar abscess. The part of bone destroyed by 
the abscess absorbs comparatively little of the rays, so that 
these darken the corresponding part of the sensitive film to a 
degree more or less marked, according to the size and depth 
of the abscess cavity. Writers have recently been differen- 
tiating more and more between "alveolar abscesses" and 
" granulomata" and their appearance on the film in contra- 
distinction to that of some forms of cysts. The differential 
diagnosis in these cases is not always as simple as it was 
hitherto considered. 

An acute alveolar abscess may not be at all apparent on 
the film, as in the preliminary stages no bone decalcification 
has as yet taken place, consequently no radiolucent area 
will show on the film. Pus may have accumulated under 
the periosteum or gingiva after having pierced the outer 
plate of bone, through one or more minute openings, espe- 
cially in the maxilla, without appreciable destruction of the 
periapical bone. But not until decalcification has progressed 
sufficiently and a cavity has finally developed at the apex 
or side of the root does this change announce itself by a 
correspondingly radiolucent area. 

According to Thoma proliferating periodontitis, caused by 
poisons and ferments which stimulate new growth, is gener- 
ally the first stage of alveolar abscess and granuloma, bringing 
about thickening of the pericemental membrane and conse- 
quently the appearance of a radiolucent line surrounding the 
end of the root. The pressure of this thickened membrane 
upon the surrounding bone causes its gradual decalcification 



180 THE X-RAYS OR RONTGEN RAYS 

and absorption, producing the so-called abscess cavity. The 
term granuloma should, in the writer's opinion, naturally 
denote the next stage, that of an effort by nature, albeit 
pathological, to restore lost substance by the process of 
granulation inside the thickened membrane. 

Dieck has made the distinction between cyst and abscess 
or granuloma, as they appear on the film, in that he describes 
the walls of the granuloma as more or less undefined and those 
of the cyst as sharply outlined. As cysts are now believed 
often to develop from epithelial granulomata, this distinction 
seems no longer entirely satisfactory. Besides, conditions of 
surrounding tissues may obtain which may cause the walls 
of the cyst to appear less defined. 

According to Thomas, 1 if the abscess does not fill with new 
bone tissue, "a walling off of the abscess cavity and the 
formation of a sterile cyst about the apex of the root may 
occur. It may be surrounded by a smooth white border, 
which demarcates it sharply from the surrounding cancellous 
bone. This line is somewhat similar to, but less dense than 
the white border of the antral shadow." 

In interpreting radiographs we should try to differentiate 
between an area of lessened density and a direct cavity, 
which, covered perhaps by a thin layer of dense bone, may 
present the same appearance. We should make it clear 
to ourselves that the radiograph generally presents a sort 
of composite shadow of superimposed successive layers of 
healthy soft tissue, normal and diseased bone, products of 
decomposition, pus, serum and any substance lying between 
the outer skin and the film or plate, and that only a compari- 
son between the appearance of the area in question and the 
surrounding structures and adjacent teeth can give us a 
means of determining the degree and extent of the lesion. 

It is always advisable to take more than one radiograph in 
cases of suspected alveolar abscess, especially in the region of 
the bicuspids and molars, as owing to overshadowing by other 
roots, etc. (for example in the case of abscess around apex 

1 J. F. Thomas, Dental Summary, June, 1917, p. 417. 



THE USES OF THE X-RAYS IN DENTISTRY 181 

of the palatal root), the radiolucent area, while not being 
visible on the first film, may show very distinctly if the 
radiograph is taken from another angle. 

A radiolucent area will not necessarily be a proof of an 
active focal infection, for the treatment may have taken place 
and nature not yet had time to form new bone tissues in the 
cavity. The appearance of an area more radiopaque than 
the surrounding structure will of course point to over- 
calcification resulting from inflammatory stimulation, as in 
the healing of fractures. This will show the pathological 
process to have taken place at a previous date. 

The appearance of absorption at the root end as well as 
exostosis or ankylosis with absorption of the pericementum 
are indicative of a process of longer standing. These con- 
siderations, in connection with the clinical anamnesis of the 
case, may aid in forming a correct diagnosis. 

In determining the presence of granulomata of the upper 
first bicuspids the direction of the rays should be more from 
the front than with the second ones, so as to bring out, if 
possible, the apices of both roots. Many faulty diagnoses 
have been made by not considering the probable overlapping 
of the buccal over the palatal root. 

For upper molars, the rays should be directed more from 
above, if it is desired to bring out the palatal root on the 
film, and more horizontally in order to show the buccal roots. 

Lowe advises directing the rays a little from behind in 
taking first and second upper molars, in order to avoid the 
shadow of the malar bone. 

It is of course advisable to take radiographs from time to 
time after the treatment of alveolar abscess, by apiectomy 
or otherwise, in order to determine the degree of calcification 
that is taking place. These radiographs should of course all 
be taken under the same conditions of tube resistance and 
current strength, as well as time of development and strength 
of developer. 

The disconcerting discoveries of recent years, since Hunter 
first drew the attention of the medical and dental world to the 
intimate causal relations between oral foci of infection and 



182 



THE X-RAYS OR RONTGEN RAYS 



numerous systemic diseases of hitherto obscure etiology, have 
served to bring about the most desirable cooperation of the 
medical and dental professions. This immense progress could 
never have been achieved without the help of radiography, 
and this alone is enough to give the Rontgen rays a high rank 
in the list of methods of diagnosis. 

The history of each case should be carefully studied and 
considered; a dark shadow does not necessarily mean the 
presence of an active infected focus, especially in the cases 
that have been previously treated by competent dentists 
and when nature has not yet filled up the cavity with new 
bone tissue. 




Fig. 



On the whole every radiolucent area at the end of a root 
should be regarded as a potential factor of disease and 
eliminated by treatment, apiectomy or extraction, unless 
considerations such as mentioned above are proved to exist. 
The bacteriological examination of such periapical areas in 
all doubtful cases should constitute a decisive factor in deter- 
mining the course of treatment. 

Fig. 99 is an illustration of both destruction of bone and 
absorption of the end of the root of the affected molar. 

One or more broaches inserted into the nerve canal and 
extending through the apical foramen of the affected roots 
will often show the operator through which of them com- 
munication with the abscess cavity has been established. 

The writer has at times seen cases of marginal abscess on 
the sides of the roots of teeth with living pulps; these also 
may be shown on the radiograph. 



THE USES OF THE X-RAYS IN DENTISTRY 183 

The variety of cyst in question is generally the radicular, 
in contradistinction to the follicular; it occurs oftener in the 
superior than in the inferior maxilla. 





i i 



Fig. 100. — Abscess on lower molar 
showing extensive destruction of 
bone. 



Fig. 101. — Abscess involving 
two roots of molar. Negative. 
Taken by J. J. Lowe, Boston. 





Fig. 102. — Abscess cavity involving 
upper canine and first bicuspid. 



Fig. 103. — Cyst involving upper 
lateral canine. Taken by J. J. 
Lowe, Boston. 



Radicular cysts are generally of traumatic origin and 
in many cases the age of the patient at the time of the 



184 



THE X-RAYS OR RONTGEN RAYS 



accident may be fairly accurately determined by the degree 
of arrested development of the root and the size of the canal, 





Fig. 104. — Broach inserted into Fig. 105. — Connection with an- 

root canal and protruding into trum shown by introduction of 
abscess cavity. broach. 




Fig. 106. — A case of fistula opening on the cheek and accompanied by 
considerable loss of bone. 




Fig. 107. — A case of fistula opening on the chin with probe inserted through 
fistulous opening. Taken by J. J. Lowe, Boston. 






THE USES OF THE X-RAYS IN DENTISTRY 185 

if the accident occurred at a time before the root of the tooth 
in question was fully developed. 




Fig. 108. — Dentigerous cyst in mandible containing two biscuspids which 
were subsequently removed. Radiograph also shows impacted second molar 
and wisdom tooth occupying a horizontal position. 




Fig. 109. — Showing arrested development of root. 



The approximate date of lesions of a traumatic nature, 
resulting in pyorrhea or absorption may be established fairly 
conclusively by the .r-rays. Fig. 109 illustrates a case of 



186 



THE X-RAYS OR RONTGEN RAYS 



arrested development of the right central incisor which shows 
the flaring of the canal at the apex, causing slight hemorrhage 
upon insertion of the broach and interfering with the stopping 
of the canal with gutta-percha. The age of the patient at the 
time of the accident, according to her statement, was verified 
by the radiograph. 





Fig. 110. — Showing extensive 
destruction of alveolus around 
lower molar. 



Fig. 111. — See page 188. 



V. The dentist or prophylactic specialist should not be 
satisfied to undertake the treatment of any pronounced case 
of pyorrhea without first determining by .r-ray diagnosis the 
degree of destruction of the alveolus surrounding the teeth 
in question, and should compare this first radiograph with 
one or two taken several months or even years after treat- 
ment. The presence of calculus on the roots is also in many 
cases readily discernible on a good .r-ray film, but much 
experience in the selection of the tube and in the time of 
exposure is necessary to detect this in every case, whereas the 
amount of absorption is apparent on all but the very poorest 
films. 

The appearance of a slightly radiopaque streak extending 
through the anterior teeth (especially the lower), and giving 
rise to the suspicion of a pulp stone, may be caused by a 
ring of hard calculus extending around the neck of the tooth 
or lower down on the root. In these cases the unmistakable 
radiopacity caused by the calculus usually also shows on the 
approximal surfaces of the teeth in question, thus facilitating 
diagnosis. 



THE USES OF THE X-RAYS IN DENTISTRY 187 

The taking of a stereoradiograph is often of use in deter- 
mining the extent of destruction of the alveolus (Figs. 112 
and 113); moreover, the operator can in some cases more 




188 THE X-RAYS OR RONTGEN RAYS 

easily distinguish by this process whether calculus has been 
deposited upon the palatal or labial wall of anterior teeth. 

A sharp radiograph will show the presence or absence of the 
linea dura of the alveolus on the approximal wall of a tooth 
affected with pyorrhea, and thus enable the operator to 
judge better of the chances of successful treatment. Of course 
this does not apply to the lingual or labial wall of the root. 

It has been observed that in many instances after treat- 
ment of pyorrhea the condition of the teeth and surrounding 
tissues has, clinically speaking, greatly improved; that is to 
say, the flow of pus has stopped, the teeth have become firm, 
the pockets closed up, and the gums tightened around the 
roots; still the radiograph taken at this time may indicate 
hardly any restoration of bone. The writer has often 
remarked this appearance and can only explain it by the fact 
that prior to the filling up of spaces by new bone structure 
the toned-up connective tissue and mucous membrane form- 
ing the gum substance cling to the pericementum so tightly 
that the tooth has in reality become vastly firmer, although 
the actual formation of bone does not take place until 
much later. This condition, however, does not show on the 
radiograph, probably because connective tissue and the 
pus-containing pockets shown on the first film present 
approximately the same degree of resistance to the .r-rays. 

A radiograph, taken perhaps for an entirely different pur- 
pose, occasionally shows a tooth apparently hanging in midair 
that clinically seems comparatively firm (Fig. 111). There 
seems, however, every reason to assume that when a pyorrhea 
case has been skilfully and successfully treated, restoration 
of bone around the roots and in existing pocket cavities takes 
place; this depends, however, on the age of the patient and 
the severity of the case. 

VI. The determination as to whether a broken-off instru- 
ment in a root canal has or has not perforated the side 
of the root is not always to be arrived at by taking a single 
radiograph, as, for instance, the protruding part of a broach 
perforating the buccal or palatal wall of the root of an upper 
incisor can probably not be detected as such if the rays are 



THE USES OF THE X-RAYS IN DENTISTRY 189 

directed from the front, whereas, if striking the tooth more 
laterally it may easily become visible. A stereoradiograph is 
often of value in such cases. 

The fact that a radiograph is a composite shadow picture 
of the various layers penetrated by the rays, should never be 
lost sight of and unless the protruding portion of the instru- 
ment or pivot is seen outside of the margin of the root, the 
most aggravated case of perforation might appear merely as 
a comparatively harmless piece of metal lying within the canal. 
Of course the presence of a fragment of a broach is never an 
agreeable discovery in a root canal, but when both radio- 
graphic and clinical examination show it to be well inside 
of the roots, the probabilities are in favor of its doing no 
great harm if entirely incorporated in the canal filling. In 
upper first bicuspids a perforation between the roots is 
usually not easy to detect by means of the .r-rays. 





Fig. 114 



Fig. 115. — Broken off broach 
which has passed through apex of 
root. Taken by J. J. Lowe, Boston. 



Fig. 114 shows a broken-off root-canal drill perforating the 
side of the root. 

VII. Fractures of roots can readily be recognized by radio- 
graphs. These should in all cases be taken after any trau- 



190 THE X-RAYS OR RONTGEN RAYS 

matic lesion to teeth or jaws, and can often save the surgeon 
or dentist much time and trouble. One case that occurred 
in the writer's practice recently serves to illustrate this fact 
clearly. An officer had received a blow against his front teeth 
by a vigorous toss of his horse's head. The mesial corner of 
the left central was broken off and the right one was fractured 
so that the labial surface was split and hung only by a piece 
of gum. After its removal the pulp was found to be intact 
and not exposed, that part of the tooth being apparently as 
firm as the other teeth. In order to avoid killing the pulp 
it was decided to make a platinum cap with porcelain facing, 
and this was set and no inconvenience experienced for the 
first two weeks. But then the patient returned with a 
feeling of uneasiness and looseness of the cap, which made 
an .r-ray seem desirable. This showed another horizontal 
fracture about 6 mm. from the apex, which was aggravated 
by the cap, causing the two parts to become more and more 
disconnected, and ending in the condition described above. 
Now, the root upon which the cap was cemented seemed 
perfectly normal, but had an .r-ray been taken at once, both 
patient and operator would have been spared much trouble 
and annoyance, for the root would have been extracted at the 
beginning. The film, though plainly revealing the condition 
described above, unfortunately did not show strong enough 
contrasts to be reproduced here. 

VIII. The existence of pulp stones may be demonstrated 
by the Rontgen rays, showing as a body of approximately 
the same density as the dentine, and occupying a part of the 
otherwise dark-appearing pulp chamber. These pulp stones 
are by no means always apparent and it requires much 
experience and technic in choosing a tube of proper vacuum 
and timing the exposure correctly to obtain satisfactory 
results. G. M. Brown advises using a rather softer tube for 
this purpose. The radiopacity of a pulp stone will usually 
be greatest at its centre, gradually diminishing toward the 
periphery. One circumstance should not be overlooked, and 
that is the possible presence of buccal stoppings of decep- 
tive size, as they are liable to dampen the operator's joy on 



THE USES OF THE X-RAYS IN DENTISTRY 



191 



considering himself the happy possessor of a genuine pulp 
-tone .r-ray. a thing of comparatively rare occurrence in the 
practice of the general dental practioner who limits his .//-ray 
work to his own practice. 

IX. One of the most discouraging sights, and one that 
unfortunately occurs in the best of practice.-, is that of caries 
under crowns and caps or fillings that extend under the gum. 
In cases of suspected approximal cavities in very crowded 
teeth where no fillings have yet been inserted, and which 
could hitherto be detected only by wedging, the writer has 
repeatedly been able to detect caries by taking a radiograph 
of two or more of the teeth in question. 





Fig. 116 Fig. 117 Fig. US 

Figs. 116. 117 and US. — Caries under caps and old stoppings. 



Before setting any gold inlay extending well under the gum. 
an .r-ray. with inlay held in place, should always be taken 
and will save much trouble in smoothing away "catches" 
subsequently. 

X. In affections of the antrum the .r-rays often form an 
important link in the chain of diagnostic factor.-, and a radio- 
graph should certainly be taken if there remains any doubt 
after illuminating the oral cavity and resorting to the usual 
mean- of diagnosis. The radiograph should be taken with a 
large plate postero-anteriorly. the face of the patient firmly 
pressed against it. and the expo.-ure should be shortened by 
the use of a good intensifier. The tube should have a 
resistance of 10 to 12 Wehnelt or 7 to 8 Bauer qualimeter. 



192 THE X-RAYS OR RONTGEN RAYS 

Empyema of the antrum will be indicated by a lighter appear- 
ance of the affected side, as the rays will be absorbed more 
readily by the pus-containing secretions. There are, how- 
ever, so many cases in which the density of normal bone may 




Fig. 119 



vary considerably on either side, that the radiograph alone 
should not be considered sufficient. Fig. 119 shows a case of 
empyema of the right antrum and frontal sinus. The affected 
antrum appears darker on the print owing to the absorption 



THE USES OF THE X-RAYS IN DENTISTRY 193 

of the rays by the pus-containing fluids. On the primary 
plate, of course, the appearance is reversed. The patient 
had not removed her artificial dentures. 

A skiagraph may also be taken with a large plate or film 
in the mouth held between the teeth, the rays being directed 
from above, but the presence of the bicuspids and molars is 
likely to preclude a clear image of the parts in question. 
Should the upper jaw, however, be edentulous, or at any rate 
so far as molars and bicuspids are concerned, the radiograph 
taken in this manner and showing at least a part of the 
antrum of each side, may be a very valuable help to diagnosis. 
The presence of roots, dentigerous cysts, or even foreign 
bodies in the antrum may of course be easily demonstrated in 
this way. Dieck reports a case in which a bicuspid root was 
forced up into the antrum during an extraction. In this 
connection it will be well to bear in mind the possibility of 
misinterpretation referred to before, which may be brought 
about by the inclusion of the root-ends on the film within the 
image of the antrum, while the root itself may occupy its 
normal position in the maxilla. 

In determining whether a root actually or only apparently 
extends into the floor of the antrum three possibilities should 
be considered : 

(a) Whether the root is situated buccally or palatally of the 
antrum. 

(b) Whether there is actual perforation of the floor of the 
antrum. 

(c) Whether the root, while extending into the antrum, is 
still covered by convolutions of alveolus, periosteum and 
pericementum. 

In this case a thin radiopaque line, representing the fold of 
alveolus, next to this a fine radiolucent line, the periodontal 
membrane, should be visible. Only a sharp radiograph will 
show this. 

A sure means of verifying a radiographic diagnosis of 

empyema of the antrum, and one which the writer has not 

often seen mentioned in connection with the transillumination 

of the oral cavity with the electric mouth lamp, is the pupil 

13 



194 



THE X-RAYS OR RONTGEN RAYS 



test. The diagnostician should ask the patient to look at 
him, and then in another direction, repeatedly, while the 
mouth lamp is illuminating the oral cavity (of course in a dark- 
ened room). The lips should enclose the tube containing 
the bulb. If both pupils appear luminous, like a cat's eyes 
in the dark, there is conclusive proof of the non-existence 
of empyema. Should, however, only one pupil be visible it 
would strongly point to empyema of the opposite side, as the 
transparency of the pupil over the affected antrum would be 
impaired by the presence of pus. In some cases especially in 
men, the bone structure is so dense that the pupils would not 
be visible even under normal conditions, but with a strong 
mouth lamp they will generally show through a healthy 
antrum. The writer has found this a most reliable test. 




Fig. 120 



XL The subject of facial neuralgia is one that extends 
into so many different territories that its thorough con- 
sideration is of course out of the question here. Suffice it 
to say that its origin is often of so obscure a nature, while 
the trouble itself may become a source of intense agony to 
the patient, that no possible aid to its diagnosis should be 
neglected, and an a>ray may reveal conditions (chiefly of 
impacted teeth) the removal of which may restore health 
and comfort to the sufferer. Fig. 120 shows an impacted 
left lower second bicuspid pressing against the first molar 
root and causing absorption and all the symptoms of severe 
neuralgia. The patient has experienced no more trouble 
since the extraction of the molar. Upson, among others, 
strongly urges the radiographic examination of the jaws and 



THE USES OF THE X-RAYS IN DENTISTRY 195 

teeth of all patients suffering from mental disorders, even 
if no direct indication of their dental origin is apparent. 1 
Exostosis of roots is also one of the causes of neuralgia which, 
before the era of the Rontgen rays, were a source of the 
greatest difficulty to the diagnostician, often leading to the 
extraction of one tooth after another until the exostosed 




Fig. 121 




Fig. 122. — Taken by Dr. H. F. Hamilton, of Boston, Mass., shows a marked 
degree of condensing osteitis or hypercementosis. The pericemental mem- 
brane has been almost entirely obliterated and the teeth appear ankylosed. 
Patient is suffering from neuritis in one arm. According to Price, con- 
densing osteitis of the roots is often coexistent with general arthritis. 

ones were revealed and removed, whereas now an .r-ray 
easily shows us the seat of the trouble. Osseous deposits on 
the wall of the pulp chamber causing pressure on the pulp 
are also often detected by the Rontgen film. Fig. 121 shows 
exostosis on roots of both bicuspids (also an ill-fitting cap on 
the first molar). 



Dental Cosmos, May, 1910, p. 525; May, 1912, p. 954, 



196 THE X-RAYS OR RON T GEN RAYS 

XII. Necrosis and osteomyelitis in their different stages 
afford the .r-ray an opportunity of proving its value as a 
diagnostic factor. At first, according to Pfahler, a trans- 
parent condition of the bone is apparent, owing to the dis- 
turbance of the fine net-work of cancellous structure, caused 
by the destruction of bony elements. The sequestrum, which 
on the film appears light, surrounded by a dark area of 
decalcified bone, is usually easily recognized and its location 
and removal is thus facilitated. 

The appearance of necrotic and osteomyelitic portions of 
bone on the radiograph may prove confusing to the average 
dentist and such conditions should in the writer's opinion, 
not be diagnosed by the ^-ray alone. As alveolar abscess is a 
simple form of osteomyelitis, the appearance of the latter on 
the radiograph in its first stages is identical with that of 
the attacked portion of bone in ordinary alveolar abscess. 
From this, its simplest form, osteomyelitis shows destruction 
of greater portions of bone interspersed with denser areas 
due to sporadic inflammatory stimulation of bone growth. 
There may be sequestra surrounded by newly forming bone. 
Periosteal proliferation may also causei: thickening of the 
cortical layer of the bone. 

XIII. For the diagnosis of tumors the Rontgen rays have 
been used in many instances with success, and although the 
dentist would naturally not be very conversant with the dif- 
ferential diagnosis of these dangerous diseases, the appearance 
of a certain transparency of the bone on the photographic film 
may serve to arouse his suspicions and determine him to call 
in a pathologist or surgeon while there is still a possibility of 
successful operation. Pfahler says: 1 " Tumors of the lower 
maxilla are shown by a disturbance in the cancellous tissue, 
at first consisting merely of an absorption of the calcium 
salts, resulting in a greater transparency, then followed by 
more complete destruction. This disease is not definitely 
outlined as in necrosis, fading gradually into healthy bone, 
and is often associated with the formation of new tissue. 

1 Dental Cosmos, September, 1911, p. 1084. 



THE USES OF THE X-RAYS IN DENTISTRY 197 

Carcinoma seems to cause more destruction of bone and less 
new tissue than sarcoma. Most of the primary tumors seem 
to be sarcoma, but the metastatic are most likely to be 
carcinoma. Not only the character but the extent of the 
disease may thus be determined, and thus material assist- 
ance secured in outlining treatment." In differentiating 
between exostosis and malignant bony growths, Shenton 1 
emphasizes the regularity and uniformity of the former in 
contrast to the ragged and spotty appearance of the latter. 

As regards the differential diagnosis of cysts and some forms 
of malignant tumor (according to Thomas 2 ) , almost the entire 
jaw may be absorbed, in the case of the former, except for a 
thin cortical shell. 'The diameter of the bone may be 
markedly increased without the continuity of the shell being 
broken, unless by trauma." 

In the case of malignant tumors "there is a tendency to 
break through the cortex and involve the soft tissues at a 
relatively early stage." 

XIV. Fractures of the jaws also offer a field of usefulness 
for the radiograph which should be welcomed by the dental 
surgeon. Prior to the adoption of any treatment, an x-ray 
should be taken to indicate the proper course to be pursued ; 
whether a splint or wire ligature should be applied and in the 
latter case where the bone is strong enough to be perforated 
so as to introduce the wire. According to Pfahler, fractures 
of the jaws are liable to occur at the places weakened by an 
extensive abscess cavity which again affords the liability of 
infection to the fractured area. The radiograph shows at 
first a dark, irregular line on the film, followed in later 
exposures by its gradual disappearance through the formation 
of normal bone. Non-union is of course also apparent on the 
film, and is indicated by the persistance of the dark area and 
formation of sequestra. 

In cases of fracture of the jaws, especially those caused by 
gunshots, stereoscopic radiographs are of great value in 
helping the surgeon to obtain a clear image of the line and 

1 Disease in Bone and its Detection by the X-rays, 1911, pp. 64, 68. 

2 Dental Summary, June, 1917, p. 417. 



198 THE X-RAYS OR RONTGEN RAYS 

depth of the fracture and the position of the fragments and 
sequestra. The plates can be beautifully viewed in the 
various stereoscopes on the market. Many instruments and 
methods for localizing bullets, fragments of shell or other 
foreign bodies have been devised that have proved very 
valuable in this war, some in connection with radiostere- 
ography, others with double radiography. 

XV. When one considers the number of cases in which the 
dentist, especially one occupying himself largely with crown 
and bridge-work, may experience the pang of suddenly 
seeing a band or post disappearing down the throat of his 
patient, one can only wonder at the comparatively few 
instances recorded. But if it be only once in a lifetime, it is 
enough to make the dentist thankful for possessing an x-ray 
outfit, if for no other purpose than to be able to locate the 
object so as to facilitate its removal before it is too late. A 
surgeon with the necessary instruments should be summoned 
so as to be at hand when the plate has been developed. 

B. 

I. The value of determining the length, shape and direc- 
tion of roots for crown and bridge- work is so self-evident that 
it requires no further remark, except to refer the reader to 
Dieck's and Ottolengui's methods of measurement with a 
broach, which have been already described. 

Fig. 123 shows the correct direction of the drill in prepar- 
ing the root for a temporary pivot tooth, while in Fig. 124 it 
is not difficult to see the advantage an x-ray would have 
afforded if taken while fitting the post of the crown. 

II and III. The determination of the degree of perfection 
attained in root-canal filling is another field for the .T-ray and 
one which does not always afford an unalloyed pleasure to the 
operator, no matter how conscientious he maybe in his work, 
for what dentist has not had the experience of occasionally hav- 
ing failed to fill a canal to the apex, which without the detective 
x-ray would have satisfied his conscience entirely? It will 
certainly help to show up the operator "who always succeeds 



THE USES OF THE X-RAYS IN DENTISTRY 199 

in filling every root canal to the very apex, no matter how 
small or crooked it is." On the other hand, the .r-ray has that 
comforting feature in that it shows that an innumerable 





Fig. 123. 



-Diagnosis of direction 
of canal. 



Fig. 124. 



-Result of not diagnosing 
bv x-ray. 



quantity of roots treated by conscientious and skilful men 
have not been filled to the apices, but are, so far as we can 
judge, doing as well as if this ideal had been possible of attain- 
ment. This is not meant as a plea for careless root-canal 
filling, but to show that where manual skill fails to accomplish 





Fig. 125 Fig. 126 

Figs. 125 and 126. — Result of not checking up while drilling out root 
canal for post. Taken by J. J. Lowe, Boston. 

the impossible, Nature often takes care of things herself. 
The writer certainly considers it more advisable to treat 
minute remnants of nerve filaments in roots found by the 



200 



THE X-RAYS OR RONTGEN RAYS 



radiograph to be curved, as a more or less negligible quantity, 
after having sterilized them as well as possible, than to run 
the risk of drilling through the side with a Gates-Glidden or 
Beutelrock root-canal drill unless other indications point 
to apiectomy or extraction. The fact that gutta-percha as a 
root-canal filling is most desirable has also been proved, it 
would seem conclusively, by the £-ray, for the writer has in 
several cases seen how kindly nature takes to it even when it 
has been pushed through the apex, as appears in Fig. 127. 
In this case the root filling of the canine that has been 
inserted six or seven years previously, was not the cause of 
the taking of the radiograph, the gutta-percha not having 
caused the slightest inconvenience. Rhein, indeed, in filling 
root canals makes a special point of "encapsulating" the 
periapical area of the root with gutta-percha. 





Fig. 127. — Gutta-percha extending 
through apex. 



Fig. 128. — Gutta-percha extend- 
ing through apex. Taken by J. J. 
Lowe, Boston. 



Fig. 129 shows extensive absorption of the end of left upper 
canine root. The protruding part of the gutta-percha root 
canal stopping has evidently assumed a nearly horizontal 
position. 

The objection to paraffin as a root-canal filling on account 
of the inability to distinguish it on the radiograph has been 
met by the addition of bismuth which makes it show on the 
film, although perhaps not quite as distinctly as gutta-percha, 



THE USES OF THE X-RAYS IN DENTISTRY 201 

and for this reason it is recommended for the purpose by 
Prinz on account of its non-irritating qualities. Indeed the 
tissues take most kindly to it. 




Fig. 129. — Absorption of root and gutta-percha protruding. 

The conclusions often arrived at upon examination of 
radiographs taken to determine whether or not a canal has 
been filled perfectly, are not always correct, for a perfectly 
filled canal may present the appearance of an imperfectly 
filled one, if the rays are directed a little too much from above 
or below, as the case may be. Either the labial or lingual 
side of the apex may protrude, on the film, beyond the end 
of the filling so as to mislead the observer, as the following 
diagram will illustrate. 




Fig. 130. — p, plate. Arrow shows direction of rays, 



This is one more reason for taking more than one radio- 
graph from different angles, or stereoradiographs, in case of 
the least doubt. 



202 THE X-RAYS OR RONTGEN RAYS 



DEVELOPMENT OF RADIOGRAPHS. 

One of the very important factors in obtaining a good 
radiograph is its development, and much could be written 
on this subject. 

In the first place an absolutely light-proof dark-room, 
however small, is a necessity, except in the case of those 
who use a light-proof muff and developing tank. The writer 
considers that the advantage of developing in complete 
darkness, as is the case with the muff, are offset by the dis- 
advantage of being unable to observe the process of develop- 
ment by red light in the dark-room, and even if the rapid 
films may suffer to some small extent from red light, the 
operator can shield the tray, so as to make this a negligible 
quantity. 

The conditions under which all exposures are made in 
dental radiography cannot, theoretically at least, be always 
the same, so as to justify a uniform time of development. 
Nevertheless good work is being done with these muffs, for 
if one film upon examination is found to be under-developed 
while the other remains covered up, the development of the 
latter can be prolonged. 

Illumination of the developing pan by a mild red light 
from beneath, as used by Lowe, is pleasant to the eyes of the 
operator. By covering the pan with a tight-fitting cover the 
process of development of one film may be prolonged while 
its duplicate is examined in the fixer by ordinary electric 
light, and the best one chosen. 

A developer which ensures excellent results is the Eastman 
£-ray developer. It is sold in the form of powders with full 
directions for use. The Eastman Kodak acid fixing powder 
is to be recommended as a very reliable fixer. 

The time usually recommended for developing is about 
five minutes, or until the image begins to turn gray, as in 
ordinary photography. 



PART II. 

ELECTROTHERAPEUTICS. 



CHAPTER VIII. 
ELECTRO-PHYSIOLOGICAL EFFECTS. 

General Considerations — Conduction by Ions. 

General Considerations. — Research of a purely physiological 
nature has demonstrated the existence of electrical manifes- 
tations in animals. Differences of potential of the surface 
of the body are always present and may be detected by 
delicate electrometric methods. Electrical manifestations 
are especially noticeable in some species of fish, greatest 
of all in the electric eel and the torpedo, which yield 
electrical discharges of considerable magnitude. Electric 
current is especially noticeable in muscle and nerve tissue, 
but it has been stated that it is to be found in all tissues 
of the body. This phenomenon has been tested with delicate 
galvanometers especially constructed for the purpose, and 
non-polarized electrodes. The skin has been stated to 
possess a current after it has been removed from the body 
(as for grafting), by placing a non-polarizing electrode on 
the inner side and a delicate galvanometer in circuit with 
another electrode on the outer side, as long as vitality exists 
a weak current will pass from the greater potential on the 
inner side to the outer. The healthy skin has also been shown 
to possess currents which can be excited and will flow toward 



204 ELECTRO-PHYSIOLOGICAL EFFECTS 

the portion which is negative to the greater potential. Exer- 
tion of the brain and contraction of muscle produce 
currents which can be detected by the use of electrometric 
instruments. 

The electrical currents which occur in muscles and nerves 
are of a continuous kind when in repose, and intermittent 
when in activity. Physiological experiments have been 
performed on fresh living muscle and nerves which demon- 
strate this phenomenon, but it has been stated that the 
continuous electric current flows as an effect of artificial 
condition produced by removal of the tissues from the body. 
The intermittent current can be produced by stimulating the 
tissue, when a current will flow at each contraction. 

Conduction by Ions. — In the living body when a con- 
tinuous current is applied it is conducted by the tissues of 
the body from one point of contact to the other as if the 
conduction were through a liquid, the body, being an electro- 
lyte, the current is conveyed by charges which are imparted 
to the ions contained in the tissues. Lewis Jones 1 describes 
this process as follows: " Conduction in watery solutions of 
salts (and the tissues of the body may be regarded as coming 
into this category) take place only by the conveyance or 
transport of charged particles or 'ions' through the liquid 
from one metallic terminal to the other, and without this 
movement of material particles there is no conduction in 
liquid solutions. The moving particles or ions are the result 
of the dissociation of the molecules of the salts by the process 
of solution, so that a solution of sodium chloride in water 
contains abundance of dissociated ions of chloride carrying 
negative charges and of sodium carrying positive. When 
a current is applied there is a double movement among the 
ions — a procession of the chlorine ions to the positive pole 
and of the sodium ions to the negative, every ion carrying 
its appropriate positive or negative charge, so that the 
measurement of the current by a galvanometer in the cir- 
cuit gives an accurate indication of the number or amount 

1 Medical Electricity, p. 300. 



CONDUCTION BY IONS 205 

of the chlorine ions brought to the positive pole and of the 
sodium ions brought to the negative." 

This transfer of the current by charging of the ions in 
both directions constitutes an important factor in the ionic 
effect of the current; that electro-positive ions move in 
their particular direction while at the same time electro- 
negative ions move in the opposite direction should not 
be lost sight of. 

When metallic electrodes are applied to the surface of 
the body, a migration of ions occurs at both poles from the 
surface of the electrode (metallic ions enter from the posi- 
tive pole) for this reason at the site of contact of the electrode, 
where ions are often not desired, great caution should be 
exercised to prevent the entry of deleterious ions from 
the metal or liquid electrode into the body at that point. 
Electrodes should be covered with some protecting material 
like chamois skin or lint which should be kept scrupulously 
clean; if the metal be brought in contact with the skin, 
destruction of the tissue might occur by the transfer of 
ions either from the metal or from salts in the tissues at 
the point of contact; this will be manifest by a blister or 
destruction of the tissues, a caustic effect, similar to that 
produced by plunging a metallic electrode into tissue for 
destruction of hair follicles and usually referred to as electro- 
lysis. Leduc in referring to this effect of the passing of 
the current between electrodes applied to the tissues of 
the body says: "The electrodes employed for medical 
application of electric current are either insensitive elec- 
trodes — carbon, platinum, etc. — or sensitive electrodes — 
2inc, copper, etc. — or electrolytic electrodes formed of 
aqueous solutions of salts, acids, or bases. In the case of 
the insensitive electrode, the anions, after having given 
up their charges at contact with the anode, become anhy- 
drides, which, in order to make the corresponding acids, 
carrv off hvdrogen from the tissues which they destroy — 
2C1 + H 2 <3 = 2HC1 + O— and oxygen is liberated. 

"The kations, after contact with the kathode, take the 
chemical character of the alkali metals, and carrv off the 



206 ELECTRO-PHYSIOLOGICAL EFFECTS 

hydroxyl group from the tissue, which they destroy, freeing 
hydrogen :K + H 2 = KOH + H. If we employ electrodes 
which can be acted on by the products of electrolysis, the 
phenomena at the anode consists, firstly, of the formation 
of acid, with the destruction of the tissue, and then the 
attack and dissolution of the electrode by the acid formed. 
From this there results a salt of the metal of the electrode 
which gives rise to the phenomena presented by the electro- 
lytic electrodes. When we use as electrodes electrolytes 
— i. e., solutions of salts, acids or bases — there is produced 
by the passing of the current an exchange of ions between 
the body and the electrodes. At the anode the body gives 
up its anions and receives the kations of the electrode; at 
the kathode the body gives up its kations and receives the 
anions of the electrode." 

These effects produced in the body by the passing of 
the current are identical with the electrolytic effects pro- 
duced in a cell or other electrolyte as already described. 
Ions may be invisible, their presence only being detected by 
their effect on the tissues of the body or by a secondary 
chemical combination by which they are transformed into a 
new product which can be seen. The movement of ions from 
the surface of metallic electrodes in an electrolyte, the rapid- 
ity with which they are transported, and their direction of 
penetration was demonstrated by the author in an experi- 
ment before the Odontological Section of the Royal Society 
of Medicine (vol. v, pp. 102), 1912. Metal electrodes of the 
same area and cross-section as those used by him in actual 
practice for the treatment of pyorrhea alveolaris were 
used for the experiment, which was performed as an ocular 
demonstration of the small amount of current strength 
required to instantaneously produce a movement of ions 
from soluble electrodes. To quote the experiment from 
the proceedings of the Royal Society of Medicine, vol. v, 
1912: 

"I have here two glass tubes, each G cm. long and 1 cm. 
in diameter, open at both ends, these tubes are filled with 
coagulated albumin. In one tube the albumin had been 



CONDUCTION BY IONS 



207 



mixed with a trace of ferricyanide of potassium, the other 
contains pure albumin. The tubes are placed side by side 
standing on the small platform, which has a platinum 
electrode connected by wire to the thumb-screw, to which 
is attached the negative lead wire; the other ends are in 
contact with a similar electrode which is connected with 
the other thumb-screw, to which is attached the positive 
lead wire. The albumin is the electrolyte, which, being 
white, readily shows the movement of ions as they take 
place. Two lengths of iron wire, each 2 cm. long and 1 mm. 




Fig. 131. — Ferrous and copper ions in albumin. 



thick, are placed one on each end of the glass tube con- 
taining the mixture of albumin and ferricyanide of potas- 
sium, passing along the side of the glass so that they are 
readily seen, the ends of the wire are bent over the sides 
of the glass and are in contact with the platinum electrodes. 
A similar arrangement is carried out with copper wire in 
the other glass tube which contains pure albumin. 

The reason for mixing ferricyanide of potassium with 
the albumin in the tube in which is placed the iron wire is 
that ferrous ions are invisible, but when brought in con- 



208 ELECTRO-PHYSIOLOGICAL EFFECTS 

tact with ferricyanide of potassium, Prussian blue is formed. 
Iron and copper are both soluble electrodes, and when a 
current of about 5 ma. is passed you can see ferrous ions 
and copper ions migrate from the surface of the metals, 
the ferrous ions staining the albumin a Prussian blue and 
the copper ions a light green; this takes place at the positive 
pole. At the negative pole no change takes place except 
the formation of hydrogen gas. I would draw your attention 
particularly to the rapidity with which the ions are formed 
and the depth of penetration." 

The effect produced by the passing of the current through 
this electrolyte demonstrates some of the changes which 
actually take place in ionic medication. Much more con- 
clusive experiments have been carried out by Dr. N. S. 
Finzi, 1 of London, with a view of determining the path 
which ions take when introduced into the living tissues. 
The experiments were performed on cats, rabbits, a monkey, 
and a dog. A number of various ions were introduced into 
the tissues of the animals by ionic medication, the tissues 
containing the ions were removed, and the ions stained in 
situ by saturating the tissues with a chemical which caused 
a colored compound with the ions. The results of these 
experiments are of great practical importance in showing 
conclusively the great depth of penetration of some ions. 
To quote one of these experiments as published in the 
British Medical Journal: 

"A monkey was anesthetized by chloroform and a pad 
soaked in potassium ferricyanide was placed over the front 
of its knee, the area which the solution touched being 
limited by a window cut in a piece of oil-silk. This pad was 
connected with the negative pole, that attached to the 
positive pole being placed on the back. A current of 10 
milliamperes was passed for thirty minutes, and then the 
animal was killed. Before its death, however, the knee 
was removed by cutting through the thigh and the leg, 
and was placed in a solution of ferrous sulphate. A control 

1 British Medical Journal, November 2, 1912. 



CONDUCTION BY IONS 209 

experiment was performed in which a pad of potassium 
ferricyanide was fixed on a monkey's knee for the same 
length of time, no current being passed, and the knee was 
subsequently treated in the same way. The next day 
the knee was opened, and it was found in the case in which 
the current was used that the skin, subcutaneous tissues, 
and patellar tendon over which the window had been placed 
were stained an intense blue from the interaction of the 
ferricyanide ions and the ferrous sulphate, and further 
that this blue extended right into the joint, there being 
a stained patch on the cartilage which penetrated right 
down to the bone. In the control the blue did not even 
penetrate the skin. This definitely proves that it is possible 
to introduce the ions of some substances directly into a 
joint, even into the cartilages; at any rate of a compara- 
tively superficial joint like the knee." 

This experiment is one of many performed by Dr. Finzi 
which was quite as convincing and is quoted to show that 
penetration of ions takes place equally well at the kathode 
as at the anode if the acid radicle type is applied with the 
intention of driving in that particular ion. 

The following experiment, which the author performed on 
gum, periodontal tissue and alveolus, provides definite proof 
that ions penetrate a considerable depth into these tissues 
with a very low current strength. A dog was anesthetized 
and an electrode of the size which is usually used for treating 
periodontal membrane, was wrapped with a little cotton-wool 
and moistened with a solution of 3 per cent, ferrous sulphate. 
This was connected with the positive pole of a generator, and 
pressed into the gingival trough and periodontal tissue to a 
depth of 4 mm. and a current of 5 ma. passed for three 
minutes. This was repeated at several points about the roots 
of teeth in the maxilla and mandible. The animal was killed 
by the anesthetic, and sections of the gum and bone about the 
treated portions removed. A portion of the gum of corre- 
sponding size and position, which was not treated, was also 
removed for comparative examination. All the sections were 
thoroughly washed and placed in a 10 per cent, solution of 
14 



210 ELECTRO-PHYSIOLOGICAL EFFECTS 

potassium ferricyanide for twelve hours. The ferrous ions 
(which are colorless) were by this treatment colored a Prus- 
sian blue, and were seen to have penetrated the whole thick- 
ness of gum tissue to the epithelial layer on the outer surface, 
and also passed into the bony structure to a depth of about 
15 mm. The ionized gum tissue was cut into sections and 
mounted for examination under the microscope. Sections 
were also prepared of the untreated tissue. 

The microscope revealed the fact that the ions had pene- 
trated the tissues from the periodontal membrane to the 
epithelial layer on the outer surface. 

These sections were submitted to Mr. Hopewell-Smith 
for examination and he agreed that the ionization of the 
tissues was complete and clearly shown. 

This definitely proves that ions penetrate freely into gum, 
periodontal membrane and alveolus with a current of 5 ma. 
in three minutes. 

Leduc demonstrated the penetration of ions into the 
body by using colored ions. He points out that if a solution 
of permanganate of potash be employed on both arms and 
current passed, the ions stain the tissue at the negative 
electrode, a brown punctate rash appearing at that pole, 
while at the positive pole no such staining takes place. 
The effect on the system he demonstrated by employing 
sulphate of strychnine with a positive electrode applied 
to the inner surface of the ear of a rabbit. If no current 
be passed the strychnine solution can stay indefinitely in 
position without any effect, but by passing a current tetanic 
convulsions typical of strychnine poisoning causes the death 
of the rabbit. 

The author once saw a patient suffer from alarming 
toxic effects of cocaine under the following circumstances: 
The patient, a powerful man, had an incisor fractured 
and the pulp exposed; in order to anesthetize the pulp a 
pellet of cotton-wool soaked in a 20 per cent, solution of 
cocaine was placed on it and a platinum electrode applied 
to this conveying positive electricity, the negative electrode 
was held in the hand. The current strength had risen to 



CONDUCTION BY IONS 



'11 




Fig. 132. — Photomicrograph of untreated tissue. 




Fig. 133. — Ionized tissue, showing a marked contrast. 



212 ELECTRO-PHYSIOLOGICAL EFFECTS 

0.5 ma. in about three minutes, when the patient, who had 
hardly perceived the current, began to show symptoms of 
cocaine poisoning. The application was removed at once, 
but he rapidly got worse, the heart action became feeble, 
and the patient prostrate, the effect lasted for two hours. 
It is likely that the cocaine ions were transmitted into the 
system not only through the pulp but also through the 
lacerated periodontal membrane, but it is not likely that 
more than yg- grain of cocaine was on the application, of 
which not one-half had been formed into cocaine ions. 
There was no likelihood of the drug being swallowed, as it 
was easily controlled in that position in the mouth. 



CHAPTER IX. 
PHYSIOLOGICAL EFFECTS OF CURRENTS. 

Cataphoric Effect — Electrolytic Effect — Path of the Current in the 
Body — Motor, Sensory and Special Nerve Effects — Effects of Current on 
Nutrition — Effects of Current on Salivary Glands — Resistance Effects of 
Current Passing through the Body. 

Cataphoric Effect. — The phenomenon of eataphoresis is 
dependent on the laws governing osmosis and the osmotic 
effect of a continuous electric current on certain liquids 
and compounds by which they are conducted en masse 
through a porous septum in the direction of flow of the 
current; that is, from the positive to the negative. It is 
based on the discoveries and experiments of many eminent 
workers in electrotherapeutics. Porret, in 1815, explained 
this tendency of fluids to be transported in the direction 
of flow of current, and later the investigations of Becquerel, 
Munk, Galitien, Wisse, W. J. Morton, and others have 
added light on the subject. Most modern works on 
electrotherapeutics contain some explanation of the cata- 
phoric effect of the current, but medical writers, as a 
rule, pay little attention to it, and seem to be sceptical of 
the reality of the cataphoric effect when applied to the 
body. They seem to be unable to separate it from other 
effects which take place at the same time when a current 
is passed through the body, and far more attention is being 
given at the present time to other electrolytic effects of 
the current. That this phenomenon takes place there can 
be no doubt, but to what extent it is applicable in electro- 
therapeutics from a dental aspect will be described in 
another part, at present the theory of eataphoresis will be 
dealt with. 



214 PHYSIOLOGICAL EFFECTS OF CURRENTS 

" Osmotic pressure 1 is that force which determines the 
movements and the rate of exchange between solutions 
in immediate contact or separated by membranes, more 
or less permeable. Substances in solution move from more 
concentrated regions toward regions less concentrated, while 
the fluid moves in the opposite direction. This movement 
constitutes the phenomenon of diffusion, and osmotic pres- 
sure is the motive force which animates matter in this way 
and produces diffusion." 

The rate of osmotic diffusion is influenced by conditions 
of temperature, relative degree of density, chemical action, 
and relative concentration of the separated fluids in the 
same circumstances as regards kind of separating medium 
and quantity of fluid employed in the experiment. Slightly 
higher temperature will raise the osmotic pressure; greater 
densities are slower in osmotic effect than weaker solutions; 
fluids of acid reaction are more rapid than alkalies. Osmosis 
of liquids of different concentrations follow the same laws 
which govern osmosis of gases in the spaces which contain 
them. 

An electric current passed through solutions separated by 
porous membrane, will greatly facilitate osmotic pressure in 
the direction of flow of current. 

This fact may be demonstrated by the experiment of 
placing two fluids of different densities in a U-shaped glass 
tube which is divided in the middle by a porous membrane 
which admits of ordinary osmotic effects. If the two halves 
contain the same amount of fluid, but one side a solution 
of sodium chloride and the other pure water, osmotic pres- 
sure will cause a tendency for the levelling up of the strengths 
of the solutions by the moving of the weaker solution through 
the membrane to the stronger; but if an electric current is 
passed through the liquid in circuit from the salt solution to 
the water it will be found that osmosis is greatly increased 
by the action of the current, and that the liquid on the posi- 
tive side will be forced through the separating membrane 

1 Leduc. 



CATAPHORIC EFFECT 



215 



into the negative side, increasing the bulk of liquid on that 
side at the expense of the other, and conveying molecules of 
sodium chloride with it. This is brought about by electrical 
diffusion or cataphoric diffusion, and is a simple illustration 
of the tendency of liquids to be conveyed en masse in the 
direction of flow of current. In addition to this, however, a 
formation of gases takes place at each electrode, oxygen at 
the positive and hydrogen at the negative. 





Na CI 



Fig. 134. — U-shaped tube before a 
current is passed. 



Fig. 135. 



-Effect of current on solu- 
tion in tube. 



This movement of the molecules of liquid in the direction 
of flow of current coincides to some extent with Faraday's 
law of electrolysis, which says that electricity flows with 
matter through it. 

W. J. Morton 1 has detailed a number of physical experi- 
ments to prove the osmotic effect of the current, and demon- 
strated by them that by the action of the current fluids 
move en masse in an electrolyte from the + to the — electrode. 

The author has tried many of these experiments and in 
every instance has obtained the result described, although 
he does not deduce the same conclusion from the phenomena 
in every case. 



Cataphoresis, p. 91. 



216 PHYSIOLOGICAL EFFECTS OF CURRENTS 

Repeating Dr. Morton's experiments it will be found that 
if a + electrode be placed in one side of a ball of moist clay 
and a — electrode in the opposite side and a current passed, 
drops of moisture collect about the — electrode; this is a 
physical transfer of water in the direction of flow of current. 

If a + electrode be placed in a piece of raw meat with a — 
electrode some distance away, a similar transfer of moisture 
from the tissues will take place to the — electrode, and the 
tissue will contract about the + electrode and adhere to 
it in consequence of the coagulation of albumin about the 
surface of the electrode. 

The author has done similar experiments with coagulated 
albumin, using platinum electrodes; drops of water exude 
about the — electrode and the album n contracts and 
adheres firmly to the + electrode. 

These effects may be purely cataphoric, but some other 
experiments quoted by Dr. Morton hardly come under the 
cataphoric effect; for example, if two copper electrodes be 
placed in coagulated albumin, at the + electrode a green 
stain will be produced; at the — electrode drops of water 
but no green coloring. This green stain should not be 
attributed to cataphoresis, it is an ionic effect caused by 
the dissociation of copper ions from the surface of the 
soluble copper electrode which migrate in the direction 
of the — element; the transfer of liquid to the site of the — 
electrode is brought about by cataphoresis, so that the 
two phenomena occur simultaneously. Take a hard-boiled 
egg and cut it lengthwise and remove the yolk, place the 
white in a saucer containing a solution of iodine and fill the 
hollow of the section of egg with weak starch water, connect 
the iodine solution with a negative electrode and the starch 
with a positive electrode. On passing a current the iodine 
will pass through the albumen and give the iodine test 
with starch. This can hardly be demonstrated as a cata- 
phoric effect because the reaction takes place against the 
direction of flow of current, but this is one of the experi- 
ments which W. J. Morton uses to amplify cataphoresis; 
it is, in fact, a good example of the migration of iodine ions 



CATAPHORIC EFFECT 217 

from the negative pole. Quoting further from W. J. Morton, 
"Cataphoresis is essentially a property of currents. 
The fact that the transporting power of the current 
diminishes and finally ceases, in direct ratio to the diminu- 
tion of resistance, indicates to me that in liquids we have 
to deal with what I have called a 'movable' resistance in 
contradistinction to what in solids (metals, etc.), might 
be termed 'stationary' resistances. From this point of 
view a fluid is projected or moved along in bulk simply 
because it does offer resistance." This opinion would 
seem to indicate that currents of considerable magnitude 
are required for this transfer of liquids en masse when cata- 
phoresis is carried out in living tissue. 

Some authors have pointed out that the transport of 
liquids or compounds appears to take place from the nega- 
tive toward the positive, in which case it is termed ana- 
phoresis, 1 to indicate the action at the cathode, but this 
phenomenon coincides with the ionic effect and it is probable 
that in every such instance in which substances are supposed 
to produce this anaphoric effect, the phenomenon is due to 
the migration of ions and in no way a transfer of the substance 
en masse as in cataphoresis. 

In medical electro-therapeutics very little importance 
appears to be attached to the cataphoretic effect, because 
such large currents are required for this to be appreciable, 
the electrolytic effect which is produced by the passing of 
a galvanic current through the body is regarded as the means 
of applying drugs in the ionic form rather than by cata- 
phoresis, and while both phenomena undoubtedly occur in 
some instances, it is ionic medication which is the principal 
effect obtained from the electrical energy. Lewis Jones 2 
says: "A movement of the electrolyte comparable to osmosis 
takes place under the influence of the current, and generally 
occurs in the direction of flow of the current, namely, from 
the positive to the negative poles; fluids can in this way be 
made to pass through membranes or porous diaphragms 

1 Guilleminot : Electricity in Medicine, p. 212. 

2 Medical Electricity, p. 304. 



218 PHYSIOLOGICAL EFFECTS OF CURRENTS 

against the force of gravity. It has been proposed to make 
use of this process for the introduction of drugs into the body 
through the skin, but the migration of the ions referred to is 
a more important factor in the percutaneous introduction of 
drugs by means of electric current." 

Cataphoresis has been largely used in practice by the 
dental profession, principally for producing anesthetic effect 
on sensitive dentine, pulps of teeth, and periodontal mem- 
brane with cocaine. In 1888 Dr. McGraw, of California, 
read a paper on the anesthetic effect of cocaine in solution 
with alcohol on sensitive dentine, this was among the first 
of the early writings on the dental aspect of the phenomenon, 
and many practitioners have since recorded the same effect 
with the galvanic current. 

W. J. Morton attributes all the effects of the current on 
solutions used for medication with a galvanic current to 
cataphoresis with the exception of the effect of the product of 
soluble electrodes such as copper, iron, zinc, etc., which he 
designates as " electric diffusion;" this is what is known now 
as ions of the metals which are dissociated by the action of 
the current, of this he points out with accuracy that " Another 
noticeable feature of electric diffusion of salts formed from 
soluble electrodes is that a remarkably low current strength 
suffices to set free a large amount of the metallic salts." On 
this point depends largely the great usefulness of soluble 
electrodes in furnishing antiseptic salts in the form of ions. 

The practice of anesthesia of sensitive dentine by the 
application of cocaine in guaiacol with the electric current 
has occupied the attention of a large section of the dental 
profession in America and elsewhere. This effect has always 
been attributed to cataphoresis, and with the teaching 
of such an authority as Dr. W. J. Morton no one doubted 
that this is the real effect, but the author has investigated 
this subject and after a number of years of experience 
with the current has adopted the view that the effect 
obtained when a continuous current is used on oral tissue 
is not a cataphoric effect, especially in the use of cocaine 
for the obtunding of sensitive dentine. A number of experi- 



CATAPHORIC EFFECT 219 

ments and also the practical application of the current, not 
only for the treatment of the hard tissues of the teeth, but 
more especially for the treatment of mucoperiodontal tissue, 
in which, working on the cataphoresis theory, were often 
negative in results, forced on him the conclusion that the 
current strength which it is possible to use on the tissues of 
the mouth is quite inadequate to produce the cataphoric 
effect ; that the good results obtained were from ions with an 
exceedingly low current strength. 

When working with the expectation of obtaining cata- 
phoric effects, a low current strength only being possible on 
such sensitive tissues as periodontal membrane or dentine, 
mixtures of drugs were employed which were not driven 
into the tissues en masse for the lack of sufficient current 
strength, but the effect of the current on these mixed drugs 
was to set in motion ions of their component parts. Results 
obtained in these circumstances were, to say the least, 
unreliable, but good results were invariably obtained with 
simple salts from which ions of an antiseptic nature were 
readily conducted into the tissues. An exhaustive test of 
this method has led him to the conviction that cataphoresis, 
as stated above, is never the effect. Ionic medication is 
always the only effect which is produced in the tissues of 
the oral cavity, when an electric current is used for medi- 
cation. 

It is quite conceivable that a substance like cocaine 
when acted upon by water is split up into ions and in this 
state is readily introduced by the electric current into 
the microscopic organic tissue of dentine. It is quite an 
easy matter to anesthetize the dentine and the pulp of a 
sound tooth by drilling a small hole through the enamel just 
to the dentine, and by applying -£$■ gr. of cocaine dissolved 
in water with a current strength of 1 ma. for five to eight 
minutes. The author has frequently done this to incisors 
to facilitate the operation of splinting loosened pyorrhea teeth. 
The transfer of the anesthetic in these cases is undoubtedly 
an ionic effect, molecules of water containing cocaine cannot 
be transferred en masse with so small a current. On the other 



220 PHYSIOLOGICAL EFFECTS OF CURRENTS 

hand, the author has shown by physical experiment that ions 
migrate immediately with a current strength of 0.5 ma. 

The ion is an inconceivably small particle when we con- 
sider that it is only a fraction of a molecule. It can be 
readily transferred into a conducting channel of microscopic 
dimensions such as the tubuli of dentine with comparative 
ease, and that it does travel with the current has already 
been shown in the chapter on ions (p. 46), where it was 
shown that ions are the conveyors of electrical charges, 
that they move with the current and are the means of 
conducting it, not only in the direction of flow but in the 
opposite direction. 

Electrolytic Effect. — The electric current passing through 
the body has the property of decomposing it at the sites 
of contact of the conducting media. Metallic electrodes in 
contact with tissues produce acid and oxygen at the anode 
and alkali and hydrogen at the kathode, by the decomposi- 
tion of the salts and fluids of the body, these are the primary 
effects; a complex reaction also takes place dependent on 
the kind of metal employed and the composition of the 
tissues; for example, if sodium sulphate (NaS0 4 ) is the salt 
present at the kathode, the positively charged ion Na becomes 
neutralized at this pole and combines with water in the tissues 
to form caustic soda (NaOH) and hydrogen; a secondary 
reaction takes place, the NaOH contains a positive ion Na 
and a negative ion OH, the OH is an ion which moves with 
great rapidity and also has a caustic action, it is repelled 
from the kathode and may have a destructive reaction on the 
tissues. This caustic effect is sometimes produced in the hand 
and other parts of the body; the hydroxyl ion (OH) by its 
caustic action destroys the skin and a small vesicle is formed. 

The electrolytic effect of the current is utilized in medical 
practice for producing coagulation of blood in aneurysm, 
at the anode a firm small clot is formed and an acid reaction 
produced, at the kathode a more diffused alkaline clot. 

The complex structure of an electrolyte like the body is 
productive of numerous electrolytic effects dependent on 
the kind and position of the electrode, but the acid and 



PATH OF THE CURRENT IN THE BODY 221 

oxygen at the anode and the alkali and hydrogen at the 
kathode are constant effects. In practice the electrolytic 
effects on soluble electrodes, notably zinc and copper, are of 
inestimable value for their antiseptic effects on the tissues. 

When a metallic electrode is placed in tissue, as, for 
example, a thin copper probe in an alveolar fistulous tract, 
after the current has passed for a while the electrode will 
adhere firmly to the tissues if the current is of positive 
sign; if the poles are now reversed the tissues at once 
release their contraction about the electrode and it is easily 
removed. 

Path of the Current in the Body. — When a current is passed 
through any part of the body, it is not conducted from 
one electrode to the other in a direct course, but branches 
out in curves and at right angles to the points of contact, 
the lines of current are denser at these points and radiate 
from them (see Density, p. 72). Lewis Jones, in describing 
diffusion of current in the body, says, "The path of a cur- 
rent between two electrodes placed upon the body surface 
is not to be marked out simply by drawing direct lines from 
one to the other, for the whole of the conducting tissues 
between the electrodes helps to provide a passage for the 
current, which spreads out from beneath the positive 
electrode, becoming less and less dense as it occupies a 
wider and wider sectional area of the conductor, and again 
grows denser as its lines of passage once more gather together 
to reach the negative electrode." According to this descrip- 
tion of the lines of current a positive electrode applied to 
periodontal membrane in the incisor region would show 
divergence of direction something after the lines of the 
diagram. With a small spear-shaped electrode, such as 
indicated on the diagram, the density of current is greatest 
at the very end, and radiations of current take place in all 
directions from the surface of the electrode, which is brought 
in contact with the moistened tissues. Electrodes of such 
small area and cross-section, intensify the density as already 
stated (see p. 73); for this reason a very small current 
strength produces an effect on the tissues equal to that 



222 PHYSIOLOGICAL EFFECTS OF CURRENTS 

produced by a very much greater current strength applied 
with electrodes of large area, but, of course, only acts on a 
much smaller surface. A continuous current passing into the 
tissues from an electrode which measures 2 sq. mm. concen- 
trates the flow of current from its surface to an extent which 
makes it possible to medicate the tissues more perfectly (in a 
tissue of such small resistance to current as periodontal 
tissue) with a current strength of only 2 ma. than would 
a flat electrode of 2000 sq. mm. (applied to the surface of a 
high resisting tissue like the skin) with a current strength of, 
say, 20 ma. So, also, if a large flat electrode be applied to the 
surface of the gums the density of the current is reduced and 
the penetration of medicines applied in this manner will be 
very slight with a small current strength. 




led rode 



Fig. 136. — Lines of current diffusion about a positive electrode placed in 
periodontal tissue. 

The diffusion of current in the body and effects of density 
are of great practical value in dental electrical treatment; 
the concentration of current from small electrodes permits 
of perfect means of medicating diseased periodontal tissue 
with a current strength which is readily tolerated by such 
sensitive tissues, at the same time the electrolytic effect pro- 
duced at the positive pole is usually non-productive of caustic 
effects; the effect of density is therefore a great aid, rather 
than detrimental in this method of using the current. 

Motor, Sensory and Special Nerve Effects. — When a con- 
tinuous current is passed through the living body it has the 
effect of stimulating the motor, sensory, or special nerves 



MOTOR, SENSORY AND SPECIAL NERVE EFFECTS 223 

nearest to the point of contact of the active electrode. 
When a current is applied to a motor nerve it causes con- 
traction of the muscle which that nerve supplies; in the case 
of a sensory nerve it conveys to the brain impressions of 
sensations (weak or strong) according to the strength of the 
stimulation; if the nerve trunk is an ordinary mixed nerve 
it conveys both; in the case of nerves of special sense the 
stimulation causes a response to the particular sense which 
the nerve ordinarily controls. 

The stimulation of motor nerves occurs at the closure of 
the current if the current be at least about 1 milliampere, 
and at both make and break of the circuit if the current is 
a strong one. This will depend on the position of the nerve 
stimulated; the superficial nerves will respond to a direct 
stimulation with a very small current strength, while a deep- 
seated nerve trunk will require a larger current to effect 
a stimulation and contraction of the muscle it supplies. 
Stimulation of motor nerves only occurs at make or break 
of current and is a spasmodic single contraction, which 
does not continue (except the current be a very large one) 
even though it continues to flow. 

If the current is a rapidly interrupted one, as from an 
induction coil, the stimuli to the nerve are so rapid that 
the contractions become tetanic, there is not time between 
make and break of the current to permit of relaxation or 
reconstruction, so the muscles supplied by the stimulated 
nerve contract tetanically. This effect of stimulation of 
the nerve supply to certain muscles is much resorted to in 
medical practice for practical testing of certain muscles 
from certain points called motor points, from which muscles 
are stimulated to produce contraction effects for diagnosis 
of disease, its bearing has little to do with dental treatment. 

Certain forms of discharges from high-frequency machines 
will also produce motor stimuli. 

The stimulation of sensory nerves is influenced to a great 
extent by the strength of the current and the density at 
the point of stimulation; the nature of the ions which are 
introduced at the point of contact of electrodes vary the 



224 PHYSIOLOGICAL EFFECTS OF CURRENTS 

sensation; with some the penetration at the kathode pro- 
duces more pain than at the anode, but generally the reverse 
is the case. The sensory stimulation of mucous tissue is 
productive of a feeling of pricking of a vast number of fine 
needles; on periodontal tissue, of a burning sensation. These 
sensations are increased or diminished with the area and cross- 
section of the electrode. If a small continuous current is 
passed with a very small electrode the sensation is one of 
tingling, burning at the point of contact, an impression 
which would be wholly lost with a larger electrode conveying 
the same amount of current. Interrupted currents produce 
sensations of shock, the severity of which will depend on the 
electro-motive force; if the interruptions are exceedingly 
rapid the sensation produced is a benumbed effect, that is, 
a true anesthetic effect which has been utilized occasionally 
for the operation of extraction of teeth "without pain," a 
principle which has been much questioned in some quarters 
as to its true efficiency, but which no doubt is a real anesthetic 
effect, by which sensation of pain is benumbed. 

A continuous current of 10 to 12 ma. passed with a small 
anode into the periodontal tissues in the molar region of the 
superior maxilla will sometimes cause what the patient 
describes as dizziness, but in fact is a general anesthesia effect; 
how far this can be carried it is difficult to say. The writer 
has a patient on whom he has, on several occasions, noticed 
this general anesthetic effect when a small zinc electrode is 
placed in a pyorrhea pocket between the second and third 
upper molars and a current of 10 ma. applied for about five 
minutes; for the first minute or so slight tingling pain is the 
effect of the stimulus, but soon the parts become numb and 
when the current is raised to 10 ma. for a short time, the 
patient behaves as if passing under the effects of a general 
anesthetic, but is easily roused on removal of the current, 
and described the feeling as that of dizziness; the senses of 
hearing and sight are also dulled, but respiration is not 
affected. 

The stimulation of nerves of special sense gives rise to 
effects peculiar to the sense which is dependent on the 



EFFECTS OF CURRENT ON NUTRITION 225 

particular nerve. Stimulation of the olfactory nerve gives 
rise to a sense of smell, the auditory nerve to the intensi- 
fying of sound, the optic nerve gives rise to sensation of 
flashes of light. The stimulation of the optic nerve through 
the filaments of nerves connecting it with the nerves of the 
teeth is the best example of stimulation of nerves of special 
sense. A continuous current applied to any of the teeth in 
either the maxilla or mandible, with a current strength of 
1 ma. or more passing through dentine or cementum of 
live teeth, at make and at break of current, the stimulus 
will cause a flash of light in the eye which receives the 
stimulus; this flash is very vivid and resembles lightning. 
It has long been known that current applied to the vicinity 
of the eye, as on the closed eyelid, causes stimulation of 
the retina, which produces effects of different colored lights, 
some say dependent on the pole which is used. With 
stimulation through the dental nerves the flash is always 
a bright white light, and is produced by either anode or 
kathode at the make or break of circuit. 

Stimulation of nerves of taste produces a metallic taste. 
This is noticed by patients taking galvanic baths when 
the bath comes above the shoulders. 

Effects of Current on Nutrition. — Experiments on animals 
have shown that treatment with constantly varying currents 
have the effect of increasing their weight; a comparative 
test in which some young dogs of one litter were treated and 
others not, all being fed and kept under identically the same 
conditions, those which were treated by general faradization 
improved in physical condition and gained tissue weight over 
those which were not treated. Similar experiments have 
been carried out with chickens in which it has been found 
that they improve in size and weight at a rapid rate, owing 
to stimulation by current. Rhythmical, interrupted, and 
sinusoidal currents are said to have the best effect on general 
nutrition, while continuous currents or static electricity is 
less effective. The benefits derived from general electrical 
treatment are recognized by the medical profession, and 
many forms of treatment are employed for general stimula- 
* 15 



226 PHYSIOLOGICAL EFFECTS OF CURRENTS 

tion of the body to secure improvement in certain morbid 
conditions. 

Effects of Current on Salivary Glands.— Continuous currents 
of small strength applied in the vicinity of nerve supply to 
salivary glands cause increased secretion by stimulating the 
nerves controlling the blood supply and increasing functional 
activity of the glands; copious supply of saliva will be 
excited in the sublingual glands by applying an electrode to 
the soft tissue in the region of the lower incisors, cuspids, 
and bicupids; the submaxillary glands are excited by appli- 
cation of current to the region of the lower molars, and 
the parotid glands are excited by application to the bicuspid 
or molar region of the superior maxilla. Generally speaking, 
electric stimulus to the nerve supply of secreting glands of the 
body increases secretory activity of the cells and causes an 
increase of their secretions. 

Resistance Effects of Current Passing through the Body. 
— The resistance of the body is a very complex problem; 
unlike a metallic conductor, the tissues vary in conductivity 
according to the kind to which electrodes are applied, and 
even in the same kind it varies from day to day. The skin 
offers the most resistance to the passing of current, and this 
varies according to whether it be moist or comparatively 
dry (perfectly dry skin is a bad conductor). 

Nerve, blood, and muscle are in that order the best con- 
ductors of current. Guilleminot says: "The blood plays 
an important role in the conductivity of the body. Like 
the other fluids of the body, it is composed of a solution of 
salts, acids, and bases, and of non-electrolytes, albumins, 
sugars, and fats." 

If an electrode is placed in a mucous tissue the resistance 
is much less than if the epidermis is the site of contact. 
This has been explained by Leduc by the idea of migration 
of ions, the skin being poor in ions, the interchange of ions 
from the skin to the electrode or from the electrode to the 
skin is imperfect and resistance to passing of current is 
increased ; but if the parts are saturated with a saline solution 
which is rich in ions, the contact becomes more complete by 



EFFECTS OF CURRENT PASSING THROUGH BODY 227 

the passing of ions and resistance is reduced. If the anode 
is applied to periodontal membrane with the hand as con- 
tact for the negative element, the resistance of the body is 
often found to become less as the application goes on, up 
to a point, especially if the hand electrode is kept well 
moistened or if a carbon electrode placed in saline solution 
is used and the whole hand immersed in the solution. 

Different methods have been devised for measuring the 
resistance of the body such as the Wheatstone Bridge, 
Mergier's ohmmeter, etc. These are generally constructed 
on the principle of a known E. M. F. and current strength 
from which may be calculated the resistance according to 
Ohm's law, but for all practical purposes, if it is required, 
to ascertain the resistance of a patient in circuit, it is easy 
to calculate it according to Ohm's law if the electro-motive 
force at the electrodes on the patient's body is known and 
the milliamperemeter indicates the current strength which 
is passing. 

Say, for instance, a battery or current switchboard which 
is equipped with a reliable voltmeter showing the E. M. F. 
in volts, indicates that 4 volts is producing a current strength 
of 2 milliamperes in treating a patient in circuit, the resist- 
ance of the patient is calculated 

E ^ 4 volts 

-r = R - — - = 2000 ohms. 

C . 002 ampere 

The distance the electrodes are placed apart also affects the 
resistance. Some operators in treating periodontal mem- 
brane have advocated the placing of the indifferent electrode 
near the site of ionization, on the neck or under the chin, 
in which case the resistance will be found to be much less 
than if the electrode is as far away as the hand. 

But the measurement of resistance is not an essential 
factor in the use of the current therapeutically, except in 
respect to amount of discomfort which might be caused. 
It is, however, an interesting point in the constant use of 
the current to note the variation of resistance in different 
patients and in the same patient at different times. 



228 PHYSIOLOGICAL EFFECTS OF CURRENTS 

Observations of the author led him to conclude that 
temperament or disposition of a patient has an effect on 
the resistance of the body; calm, phlegmatic, non-excitable 
people appear to conduct current better than the nervous, 
excitable, or irritable. The general health of the body 
appears also to have an influence on resistance; those in 
perfect health appear to be better conductors of current, 
and resistance is increased in those suffering from toxic 
effect of oral sepsis. The resistance of the body from the 
mouth to the hand varies considerably and is dependent 
on a number of conditions, but generally under conditions 
which may be considered almost identical, measuring it 
when an active electrode of small diameter is placed in the 
mucoperiodontal tissue and the indifferent electrode is 
moistened and held in the hand, the range may be any- 
thing between 1300 and 3500 ohms. Resistance is very 
much increased if tooth structure is included, i. e., the 
active electrode placed in contact with the dentine and 
the indifferent electrode held in the hand, and it is further 
increased if the tooth is dead; the enamel of tooth structure 
resists the passing of current completely if no moisture is 
present to conduct over its surface. 

The measurement of resistance of dentine through the 
body is dependent on such a number of circumstances 
that it is almost impossible to formulate any accurate law 
which may be said to govern all cases. Opinions vary so 
widely on this point that it is well that accuracy in this 
particular has little bearing on the therapeutic effects of 
the current in its uses for dental purposes. Allowances 
must be made, in measuring resistance, for variety in density 
of the tissue, distance between the poles, condition of the 
skin at contact of the indifferent electrode, conductivity 
of the body in different individuals, in health, or in certain 
diseases. 

Professor G. Weiss 1 places resistance of the body from 
hand to hand, in the cases of 16 men measured, at an average 
of 1300 ohms, and in 7 women at 1500 ohms. 

1 Arch. d'Electricite Medicale, 1893. 



EFFECTS OF CURRENT PASSIXG THROUGH BODY 229 

Dawson Turner 1 gives resistance from hand to hand at 
1375 ohms. 

Lewis Jones 2 gives resistance as ranging between 1000 
ohms and 2000 ohms "under conditions of medical practice 
and using salt water to moisten the skin." 

The average of 150 cases recorded by the writer from 
the periodontal tissue of the mouth to the hand holding a 
moistened electrode was 3250 ohms, but it must be noted 
that here the one electrode tried was of a very small area. 

This estimate was arrived at by recording the E. M. F. 
from the reading of a voltmeter attached to the terminal 
of a main current switchboard, and the current strength 
indicated by a milliamperemeter, the patient being in circuit 
holding a metallic electrode covered with moistened lint. 
The average was 13 volts and 4 ma. 

13 volts _„ , 

R = ^~^r. ; — = 32o0 ohms. 

0.004 ampere 

Similar measurements through dentine from tooth to hand 
gave a varied resistance corresponding with the thickness 
of the dentine and whether the teeth were alive or dead; 
one record from the surface of an erosion at the neck of a 
live tooth was 5000 ohms, another from a slight approximal 
cavity in a superior central incisor was 7500 ohms; a dead 
superior premolar with open apical foramen was 4000 
ohms. The highest recorded estimate of resistance in live 
dentine was 10,000 ohms, and this might be due to the very 
small area of the dentine and size of the electrode. It is 
evident that resistance of dentine is a variable quantity, 
and it is difficult to give a definite estimate of what it is 
as a rule. Some authors have placed it very much higher 
than these estimates here given. 

Dr. Louis Jack 3 states that "resistance of the body 
including the dental tissues varies from 10,000 to 70,000 
ohms," and the same writer, in quoting Dr. W. A. Price, 
states that author's estimate of resistance "from cavity 

1 Practical Medical Electricity, p. 188. 

2 Medical Electricity, p. 302.' 

3 Kirk's Text-book of Operative Dentistry, p. 160. 



230 PHYSIOLOGICAL EFFECTS OF CURRENTS 

to the hand" is about 25,000 ohms. It is not stated how 
these measurements were obtained, but if the estimates 
of other eminent medical electro-therapeutic authors quoted 
are correct in their calculation of resistance of the body 
from one distant part to another, e. g., from hand to hand 
(taken, for example, the highest given that of 2000 ohms), 
there is a difference of 8000 to 68,000 in these greatest 
estimates to be attributed to resistance of dentine. In the 
latter case no ordinary 18-cell battery producing E. M. F. 
of 24 volts could furnish sufficient current to overcome so 
great a resistance, consequently no current would pass. 
According to Ohm's law, 

R= " 4VOlt \ =48,000 ohms. 

. 0005 ampere 

that is, if 24 volts are required to pass a current of 0.5 ma. 
through the dentine of a tooth, the resistance would be 
48,000 ohms, which is considerably under the estimate of 
70,000 ohms. 

The writer has not found it necessary to use more than 
20 volts to pass a current of 2 ma. through the dentine 
of a live tooth from a small drill hole just through the enamel, 
with the body included in circuit to the hand. If this calcula- 
tion is correct, the resistance from tooth to hand through 
dentine in the case of 20 volts with known amperage of 
2 ma. is 

20 volts , 

R = = 10,000 ohms. 

2 ma. 

In dead teeth the resistance offered to current will depend 
somewhat on whether the canal is open at the apex and 
if there is organic matter or liquid contained to act as a 
conductor of current. If the apex is sealed with a non- 
conductor like gutta-percha the resistance will be much 
increased, as conduction will then have to be through the 
dentine and cementum, but with an open apical foramen 
and a liquid solution contained in the canal into which an 
electrode can be passed, conduction of current by this 
channel is comparatively easy, and resistance is not as great 
as it is in the case of a layer of dentine. 



CHAPTER X. 
ELECTRO-THERAPEUTIC EFFECTS. 

Ionic Medication — From a Dental Aspect — The Zinc Ion — The Copper 
Ion — -The Iodine Ion — The Silver Ion — The Cocaine Ion — The Adrenalin 
Ion — The Salicylic Ion — Advantages of Ionic Medication — Effects of Ions 
on Bacteria. 

The Therapeutic Effects of electrical currents have engaged 
the attention of the medical profession to a great extent, 
especially of late. The use of the current is not confined to 
local treatment only, but general treatment of the whole 
body for all kinds of morbid conditions; static and high- 
frequency currents are now considered of great importance. 
Stimulating, sedative, and ionic are among the medical 
therapeutic effects of different currents. In surgery the 
continuous current is largely used for cautery, light, and 
electrolytic effects. 

In Dentistry the subject of electro-therapeutics appears 
to have been sadly neglected in the past; keen interest was 
aroused some thirty years ago in America when W. J. Morton, 
of New York, published his work on Cataphoresis in which 
many valuable suggestions were made on electrical treatment 
in dentistry. Unfortunately Morton was incorrect in many 
of his deductions and the development of dental electro- 
therapeutics on those lines was practically impossible. In 
his book Cataphoresis Dr. Morton made the valuable sug- 
gestion that tubuli of dentine can be penetrated by drugs 
applied with the electric current, and in the case of septic 
root canals the driving of antiseptic drugs into the structure 
of the tooth and the sterilizing of the same is far more 
scientific and effective than the ordinary method of placing 
antiseptics in the canals. He asserts that "if cataphoresis 
is employed as a diffusing agent success will be more swift 



232 ELECTRO-THERAPEUTIC EFFECTS 

and sure. There is, in addition to all this, the possibility 
of carrying medicaments into the periodontal membranes for 
the treatment of acute infectious inflammatory conditions of 
that tissue." 1 These valuable suggestions have not been 
acted upon by the vast majority of practitioners because, in 
the first place technic was lacking, and, secondly, the subject 
of electro-physics as it pertains to therapeutics was insuffi- 
ciently explained to ensure success in the application of the 
current for the treatment of dental disorders. 

In the light of the present-day knowledge of electro- 
therapeutics, the theory of cataphoresis in dental applica- 
tion must give way to the ionic medication, and then the 
greatest stumbling-block to the success of electrical treat- 
ment of the teeth and other oral structures will be removed. 
By the lessons taught by research of Leduc, Lewis Jones, 
d'Arsonval, Turner and others, a more comprehensive 
view of the effects of the different currents on the body is 
placed at our disposal. The electrolytic effects on certain 
salts of an antiseptic nature whereby ions are transported 
into the tissues (and this with a very low current strength) 
opens up a field of usefulness to the dental profession of 
inestimable value. The natural susceptibility of the oral 
cavity to septic infection constitutes three-fourths of the 
difficulties placed in the way of almost every operation the 
dentist is called upon to perform, the burning question 
ever being how to prevent or to cure sepsis. If, then, an 
improvement on the ordinary method is placed at our dis- 
posal by the use of electric currents, it should be our duty to 
adopt it. 

Ionic Medication. — The theory of the formation and 
migration of ions and the physiological effect of ions have 
been detailed in other parts of this work, the therapeutic 
considerations, bring us to the more practical aspect of 
this electrolytic phenomena. Certain principles peculiar to 
the formation and movement of ions in the tissues must not 
be lost sight of in order to get the best results from this 

1 W. J. Morton: Cataphoresis, p. 238. 



IONIC MEDICATION 233 

method of treatment; all substances are not dissociated 
by the effect of the current; ether, alcohol, chloroform, and 
oils are some of these; it therefore would be useless to 
attempt ionization with these; the dissociation is effected in 
solutions, and only substances which contain ions in solution 
can be "ionized:" water is the only solvent which gives 
any amount of ions, though some are formed in some other 
liquids. Then, again, it is necessary to know which ions are 
electro-positive and which electro-negative, that is, which 
are driven into the tissues from the anode and which from 
the kathode. Reference has been made to this effect already, 
and it is not hard to remember that metals, alkalies, hydrogen, 
and alkaloids are repelled from the positive pole; and acid 
radicles, iodine, bromine, etc., are repelled from the negative 
pole ; the caustic effect at the negative pole (kathode) should 
not be forgotten, if by mistake the negative non-oxidizable 
metallic electrode be applied to the tissues of the mouth with 
sufficient current, formation of caustic soda, or, more impor- 
tant still, the formation of hydroxyl in the tissues might 
cause destruction of a tissue which it is desired to stimulate 
or treat with ions. 

Again, the action of the current on some drugs which 
are escharotic or have a caustic effect on tissues without a 
current, are completely changed when converted into ions. 
Iodine and chlorine are examples of this, as are also some 
strong acids. 

The local effect of ionic medication is dependent on the 
ion used. Nothing but experience can teach the effect of 
the different ions, the subject is comparatively new; never- 
theless, there is now a vast amount of literature detailing the 
action of ions of different kinds, and it is most noteworthy 
that medical experience goes to show that treatment of 
mucous tissues with ions gives the surest results: this is of 
course not to be wondered at, as it is readily perceived that 
the conduction of electrically charged atoms or groups of 
atoms must be facilitated by a soft, moist, good conducting 
electrolyte, such as mucous or periodontal tissue; whereas 
the skin, being a poor conductor, sometimes poor in ions 



234 ELECTRO-THERAPEUTIC EFFECTS 

itself, as pointed out by Leduc, penetration of ions from 
medicine applied to it is not so rapid and not so sure. 

To gather from the experience of the medical profession 
we will do well to examine the reports from one of the very 
best sources. From this many useful hints may be obtained, 
which may lead to more extensive use of ions in dentistry. 
At a meeting of the British Medical Association held in Liver- 
pool in July, 1912, Dr. Lewis Jones 1 read a paper in which he 
tabulates his own experience and that of the profession in 
general, with zinc, salicylic, chlorine, iodine, and radium 
ions; he referred to reports made in the medical journals of 
Great Britain and on the Continent of successful treatment 
of a great number of cases of local affections. Under the 
heading of the zinc ion successes have been reported in 
treatment of: 

Simple chronic ulceration of the leg. 

Bed-sore ulcerations. 

Rectal ulcerations. 

Anal fissure. 

Ulceration of the mouth. 

Pyorrhea alveolaris. 

Ulceration of the nose. 

Fistulas. 

Gynecological conditions. 

Sycosis, furuncle, acne. 

Lupus. 

Rodent ulcer, etc. 
Numerous cures are recorded of all these conditions by the 
local application of zinc ions. Dr. Lewis Jones chronicles 
three cases of chronic sores of the nasal cavities cured quickly 
under zinc ions. He says: "Two of these simulated lupus, 
but were probably staphylococcic rather than tuberculous. 
The third was an ulcer just within the nose in a middle-aged 
lady; it had persisted for several months, and healed at once 
after a single treatment." He recalls the report of a fistula 
in the lower jaw as follows: "Marquis and Fappon 2 have 

1 British Medical Journal, August 31, 1912. 

2 Arch, d'elect. mod., 1910, p. 56S. 



IONIC MEDICATION 235 

reported three successful cases of fistula in connection with 
the lower jaw. The applications were of 20 milliamperes 
of one hour's duration, and were repeated every seven days. 
From four to six applications were made, and in each case 
the zinc ionization brought to a close a troublesome condition 
which had lasted for two years or more." 

These are but a few of the very large number of cases 
reported of the healing effect of zinc ions. 

Under the heading of "The Salicylic Ion" he has collected 
a number of reports of cases of: 

1. Perineuritis and neuralgia. 

2. Painful affections of muscular and fibrous tissues. 

3. Arthritis. 

In addition to his own vast experience in the use of this 
ion for the successful treatment of this painful class of dis- 
orders, refers to the reports made by such authorities as 
Leduc, Desplates, Verney, Xorin, Circca Salse and Dawson 
Turner. 

In 1913 Lewis Jones published his book Ionic Medication, 
a concise treatise on this method of treatment, in which 
many clinical results of a convincing nature are recorded and 
many practical suggestions are made which are singularly 
adaptable to dental electro-therapeutics. I cannot too highly 
recommend this work to those who practise ionic medication. 

From a Dental Aspect. — Very little has been recorded, 
so far, of the treatment of dental diseases by ions. Probably 
the first mention in this country is that by the author (in 
discussing a paper on vaccine therapy by Dr. Eyre and Mr. 
Lewyn Payne before the Royal Society of Medicine) 1 in 
which he said: "For a long time by a method of ionic 
medication of the periodontal membrane by electric current, 
he believed he had been producing very similar results in 
the system to those claimed by the advocates of vaccine 
treatment. Ions of antiseptic salts were driven into the 
very protoplasm of the affected tissues and killed the organ- 
isms in the tissues, and he took it that the dead organisms 

1 Proceedings of the Royal Society of Medicine (Odontological Section), 
vol. iii, p. 63. 



236 ELECTRO-THERAPEUTIC EFFECTS 

were absorbed into the blood stream and had an effect upon 
the opsonins similar to that of vaccine prepared from 
cultures." 

Later in a paper read before the Royal Society of Medicine 
(Odontological Section), 1912, p. 104, the writer made the 
following statement: "It has been conclusively shown by 
many workers in electro-therapeutics that ions of zinc, 
copper, silver, and iodine have strong antiseptic properties; 
the principal advantage they possess over ordinary methods 
of applying them in treatment is that with their electrical 
charges passing through an electrolyte like the body the 
ions penetrate the cells of the tissues and (probably on 
account of a certain amount of coagulation of albumin) 
are not readily affected by absorption into the general 
circulation in the same way as drugs which are hypodermic- 
ally injected; the only question is the depth to which pene- 
tration takes place; this seems to me to depend on the 
amount of current strength which is possible and the kind 
of tissue which is under treatment; periodontal membrane, 
for example, will permit of greater penetration than the 
epidermis. 

In medical electro-therapeutics ions of zinc are successfully 
used in the treatment of such affections as rodent ulcer, 
lupus, pus-yielding sinuses, etc. In dental practice there 
are many difficult problems yet unsolved; the most difficult 
of these is the one in which ionization, to my mind, is a 
step in advance of the other methods placed at our disposal." 

The application of a number of different ions used in the 
treatment of several dental disorders was also recorded at 
that time. 

For a number of years the writer used the continuous 
electric current for the treatment of pyorrhea alveolaris, 
with the idea that cataphoresis was the effect obtained, 
the principle of mixing drugs of an antiseptic nature with 
the expectation of driving them into the affected tissues 
en masse has since proved itself to him to be erroneous, a 
certain amount of success was undoubtedly recorded, but 
failure was frequent, and in the light of present knowledge 



IONIC ME DIC AT I OX 237 

of the electrolytic effect where a current is passed, the 
writer is convinced that the good effects obtained, resulted 
from the migration of ions when solutions were used in which 
ions of metals were contained, and failure was the result of 
either neutralization of ionic effect by chemical reunion of 
ions of different kinds, thereby destroying their therapeutic 
effect (which is a doubtful hypothesis) or the migration of 
useless ions. 

In ionic medication it is advisable to dissociate a par- 
ticular ion and depend on the therapeutic value of that 
ion for the effect that is desired. For instance, if the zinc 
ion is required, a 3 per cent, solution of zinc chloride with a 
current strength of 2 or 3 milliamperes, the zinc ion will 
dissociate from the chlorine ion at the anode, the former 
migrating into the tissues. So, also, if a copper ion is desired, 
a 2 per cent, solution of sulphate of copper will furnish the 
ion at the anode. But if these solutions of salts are incor- 
porated with non-conducting and non-dissociating solutions 
like alcohol or glycerin with the expectation of passing them 
into the tissues en masse by cataphoric methods, the current 
strength necessary for this will exceed the toleration by the 
patient. 

The therapeutic effects of ions on the oral tissue are to 
my mind of such importance that it should take the place 
of the present method of treatment of nearly eA~ery form of 
septic infection of the periodontal membrane. The effect 
is that of sterilizing a septic area by the penetration of the 
ions into the tissue and the destruction there of micro- 
organisms. A great variety of different species of bacteria 
is found, not only in the pockets, but in the tissues forming 
the boundaries of the pyorrhea pockets, their action on the 
tissue is to destroy it, the pus being the product of inflam- 
mation caused by the presence of bacteria. The destruction 
of the organisms is the main object of all who treat alveolar 
suppuration. This is effectively done by passing an electrode 
into the affected pockets and by the electrolytic effect of 
the current driving ions of some antiseptic salt into the 
tissues. The depth of penetration of these ions will depend 



238 ELECTRO-THERAPEUTIC EFFECTS 

on the current strength which is available. The ions are 
deposited in the tissues, they penetrate the protoplasm of 
the cells and radiate in all directions. The effect is a local 
sterilization of an area of infection which cannot be reached 
in any other way. The practice of syringing, irrigating, 
and wiping out infected areas of tissue with antiseptics, 
with the hope of sterilizing it, is so inadequate and ineffective 
that the object is defeated and little or no permanent good 
results are obtained; this is doubtless the experience of that 
section of the dental profession which asserts that it is useless 
to treat pyorrhea alveolaris when pus persists, after a trial 
of such superficial treatment, and asserts that extraction 
should be advised. There are even those who advise the 
extraction of all teeth which are affected with pus-yielding 
pyorrhea pockets. Mr. J. F. Colyer 1 says, " In cases where 
there is considerable bone destruction, or where in spite of 
local treatment the formation of pus persists, extraction of 
the teeth must be resorted to." 

The reckless extraction of whole sets of teeth cannot be too 
strongly denounced; it is far more scientific to make every 
effort to save teeth affected by pus-yielding pockets. The 
writer is convinced that this can be systematically done by 
electro-sterilization in conjunction with surgical and other 
means as described farther on in this work. The promotion 
of asepsis in the pockets is of a permanent nature under 
favorable circumstances, and the duration of cure depends 
chiefly on the ability of the patient to carry out daily a regular 
system of hygiene of the mouth and stimulating the gums by 
brushing, etc. A few cases taken from the many hundreds 
of which accurate statistics have been kept, will be stated in 
order to make clear what is implied by the "cure of the 
disease." 

Case A.— On March 30, 1904, Miss L., aged forty-five 
years, complained of a wide space appearing between central 
lower incisors; teeth otherwise perfect. Examination revealed 
a pus-yielding pocket, 5 or 6 mm. in depth, with nodules 

1 Dental Surgery and Pathology, p. 630, 



IOXIC MEDICATION 



!39 



of calculus, of hard dark variety, attached to the approxi- 
mal surface of root. Treatment: calculus removed, root 
polished, electrical medication of pocket for eight minutes, 
tooth ligatured to next one with silk. A week later the 
periodontal membrane was perfectly healthy, all pus had 
disappeared. The patient has been seen periodically up 
to June, 1912. This pocket has neA^er been reinfected nor 
has pyorrhea appeared in other parts of the mouth. This 
is the easiest class of septic periodontal infection to treat 
by ionization, it is always readily cured provided the dis- 
placed teeth are replaced in the normal position and ligatured 
for a time. One or two ionic treatments are usuallv sufficient. 




Fig. 137. — Case B, before treatment. 



Case B.—On February 9, 1898, Miss P., aged thirty-eight 
years; six superior incisors protruding; pyorrhea pockets on 
palatal surfaces extending to a depth varying from 1 cm. 
at the centrals to 3 mm. at the cuspids; teeth loose and 
discharge considerable; all other teeth slightly affected; no 
constitutional derangement reported. Treatment: all cal- 
culus removed and protruding teeth retracted by Angle's 
method of headgear and traction bar; during retraction the 
pockets were treated with 2 per cent, copper sulphate, 3 to 
5 ma. current. Six treatments. At end of three weeks all 
signs of disease had disappeared. A retaining night plate 



240 ELECTRO-THERAPEUTIC EFFECTS 

was inserted. The case has been seen once a year up to April, 
1912, when model was taken (Fig. 138), the teeth were firm 
and gums perfectly healthy. Since then the patient has been 
seen yearly up to April, 1917, when the teeth were in per- 
fectly good condition, the disease has never recurred. 




Fig. 138. — Case B, after treatment. 

Case C. — This case is reported in the British Dental 
Journal, January, 1899, p. 2, and in the Proceedings of the 
Royal Society of Medicine, April, 1908, and will be briefly 
mentioned as a bad case of pyorrhea which has been cured 
for fourteen years. Miss R., aged twenty-nine years, con- 
sulted me in January, 1898, by her doctor's advice to have 
all her teeth extracted. History of thumb-sucking and 
mouth-breathing as a child. Superior incisors protruding 
nearly 2 cm. over the inferior incisors. Pyorrhea pockets 
on palatal aspect of superior incisors extended nearly to the 
apices; pockets of varying depth about every tooth in the 
mouth with considerable discharge of pus. Teeth exceed- 
ingly loose except molars. The patient was nervous and 
debilitated, suffering from alimentary toxemia. Treatment: 
loose bicuspid extracted; superior incisors retracted. Pyor- 
rhea pockets treated with electric current with sulphate of 
copper and iodine. In eight weeks the pyorrhea had com- 
pletely disappeared, but retraction of the incisors occupied 
about four months longer, during which time the case was 



IONIC MEDICATION 241 

seen only once a month and the treatment continued. The 
teeth are retained by a wire arch attached to a plate worn at 
night only. In 1912 the mouth presented the appearance of 




Fig. 139. — Case C, before treatment. 



the model in Fig. 140. The pyorrhea has never returned in 
any part of the mouth, the teeth have been cleaned twice a 




Fig. 140. — Case C, after treatment. 

year regularly, but only a few further treatments with ions. 
The general health of the patient improved to a remarkable 
extent, and she now possesses a useful strong set of teeth. 
16 



242 



ELECTRO-THERAPEUTIC EFFECTS 



The case has been seen recently (1917), the incisors are 
perfectly firm and free from disease; the first right upper 
molar only has been lost from caries. 

These three cases were treated, at the time expecting 
cataphoric effects, but iodine and copper were used with the 
anode and kathode, and the writer now thinks the results 
obtained were due to penetration of ions. 

Case D. — Mrs. H., aged forty-five years; every tooth of 
otherwise perfect set affected, pockets especially deep about 
the upper and lower molars where discharge was greatest. 
Teeth loose and patient's general health affected. Radio- 
graph, Fig. 141, shows condition of the alveolus. The case 





Fig. 141. — Case D. Radiographs of alveolus. 

first treated Apil, 1907, twelve treatments with zinc ions. In 
five weeks the symptoms of the disease had entirely disap- 
peared. After this one treatment a month was given until 
December 15, when the case was discharged cured. Since 
that date the patient has been seen twice a year and no 
recurrence of septic infection has occurred. 

Case E.—Mr. C, aged fifty-five years, sent by a dental 
friend on October 7, 1907. Nearly all molars, upper and 
lower, lost from pyorrhea, the incisors had suppurating 
pockets on the palatal and approximal surface; patient's 
health affected. Teeth very loose. Treatment: eight treat- 
ments with zinc ions extending until December 19, when 



IONIC MEDICATION 



243 



the periodontal membrane was perfectly healthy ; teeth firm, 
and patient's health perfectly restored. The case has been 
seen twice a year since, during which time there has been 
no recurrence of pyorrhea. The teeth were retracted to 




Fig. 142. — Case E, before treatment. 

their normal positions, as shown in Fig. 143 taken five years 
later. In 1917 these teeth were still healthy and functional. 




Case E, five years later. 



There are a few of hundreds of cases which could be 
detailed, but it will suffice to quote these typical ones. 

It is perfectly certain that in most of the cases here stated 
that such treatment as syringing the pockets or other forms 



244 ELECTRO-THERAPEUTIC EFFECTS 

of irrigation would be quite inadequate to sterilize the 
tissues infected with pus-yielding microorganisms. It is true 
that replacing teeth when displaced by the disease is in 
itself a great aid in ordinary treatment, but this is not 
sufficient to bring about a cure. 

The Zinc Ion. — The ion which appears to be the most 
sure and effective in sterilizing septic periodontal membrane 
and other forms of dental treatment, is the zinc ion. Of 
this ion Leduc 1 says: "This ion is an antiseptic of the first 
rank, and when applied electrically it can be made to pene- 
trate the tissues of the skin to any desired depth. There is 
no wound or ulcer which cannot be disinfected by its employ- 
ment, provided its surface can be reached by the electrodes." 
Many other eminent writers have classified this ion among 
the highly antiseptic, and abundant clinical evidence has 
been chronicled showing its great germicidal properties. 
Among those who make this important claim are Lewis 
Jones, 2 Finzi, 3 Marques and Pappon, 4 Bathurst, 5 Norman 
Bennett, 6 J. Forbes Webster, Fairfax Reading. The author 
has recorded in this and other works, the value of zinc ions 
in electro-sterilization and has no hesitancy in confirming 
the views of the writers mentioned, on the highly antiseptic 
properties of this ion. Recently, Prinz 7 has stated that zinc 
ions are devoid of supposed germicidal properties, but he 
has probably had little experience with this ion in sterilizing 
soft tissue and his assertion is not accompanied by any proof, 
clinical or otherwise, which might affect the evidence of the 
writers here referred to. 

The Copper Ion.— The copper ion has also a strong anti- 
septic effect and answers very well for treatment of perio- 
dontal affections; copper electrodes have the advantage of 
being readily soluble by the electrolytic solution pressure, 

1 Lesions en Medecine, Arch. d'Elect. Med., September 25, 1904. 

2 Ionic Medication, Chapter III. 

3 Proc. Royal Soc. Med., vol. ii, p. 140. 

4 Arch. d'Elect. Med., p. 568. 

6 Klin. Monatschr. f. Augenheilkunde, November, 1908. 

6 Chronic General Periodontitis, Colyer, p. 99. 

7 Dental Cosmos, April, 1917, p. 388. 



IOXIC ME DIC AT I OX 245 

even a very small current of 1 ma. seems to readily cause 
dissociation of ions, a weak solution of copper sulphate 
provides a solution electrode rich in copper ions. The copper 
ion is particularly useful for fistulous tracts such as are often 
found in the mouth, because a copper probe is easily intro- 
duced into them, a zinc electrode being often too rigid and 
too large to enter the sinus without enlarging it. 

The Iodine Ion. — The iodine ion is distinctly useful, and 
while possibly not so antiseptic as the zinc ion, seems to 
have a healing effect on the tissues. This ion is indicated 
when the tissues are nearly normal after a prolonged treat- 
ment with the zinc ion, also in treatment of the gingival 
trough in suspicious cases of threatened pyorrhea when septic 
infection has not yet caused the perceptible affection of the 
periodontal membrane. Many cases of periodontal disease 
can be averted by treatment with this ion. 

The Silver Ion. — The silver ion is effective in the treat- 
ment of pulp canals and stomatitis, aqueous solution of silver 
nitrate being a convenient form of solution electrolyte. The 
staining properties of silver nitrate debar it from use about 
the front teeth, for although the ion itself is invisible, the 
preparation in excess is liable to stain the necks of the teeth. 
It loses its caustic properties by the electrolytic action. It 
is also a useful ion for obtunding sensitive dentine of the 
exposed necks of molars or cementum of roots of teeth. 

Argyrol, a preparation of silver, possesses a distinctly 
sedative and soothing effect on gingival tissue when elec- 
trically applied. A solution of argyrol can be applied to the 
tissues without staining or caustic effects, and is useful in 
cases of hypersensitive gingivitis and sloughing of the 
papillae of the interspaces of the teeth. Argyrol, however, 
is a colloid preparation and ions do not migrate readily if at 
all, but the therapeutic effect seems constant and is worthy 
of application even if ions are doubtful in this instance. 

The Cocaine Ion. — This is readily introduced into the 
dentine of tooth structure by the current; any of the com- 
pound preparations of this drug act rapidly in producing 
anesthesia of live teeth. It can be introduced into the 



246 ELECTRO-THERAPEUTIC EFFECTS 

structure of a tooth through a tiny opening, such as can be 
made by the finest spear drill which will drill through enamel. 
As soon as sensitive dentine is exposed the cocaine ion, with 
a current strength of 0.5 to 1 ma., will anesthetize the dentine 
in a few minutes, making it possible to drill nearly to the 
pulp, when a further application will anesthetize the pulp, 
so that it can be removed painlessly. The writer has only 
limited experience with cocaine ions on soft tissues, fearing 
the toxic effects that might be produced by rapid introduction 
of the ion in so good a conducting medium, but Leduc says: 
"The ion of cocaine introduced by electrolysis produces 
effects very different from those of a solution of the same drug 
injected subcutaneously. It produces anesthesia, but it 
does not diffuse, and the anesthesia remains strictly limited 
to the surface covered by the electrode. It would appear that 
the ion is introduced by electrolysis, not into the circula- 
tion, but into the plasma of the cells." This opinion, how- 
ever, was negatived in one case in the author's experience, 
in which severe cocaine poisoning occurred when a very 
small dose of cocaine was introduced with the current 
into injured periodontal tissue in attempting to anesthetize 
the exposed pulps of a fractured tooth. Other cases of toxic 
effect of cocaine have been reported in American journals in 
which the effect was produced through the pulp alone with 
the current. 

The Adrenalin Ion. — This is readily introduced into the 
tissues affecting the vascular system in the immediate 
area of application of the anode, in a very short time, pro- 
ducing the characteristic anemic appearance. The introduc- 
tion of the drug by electrolytic method shortens the time 
required to produce the effect of blanching the tissues. 

The Salicylic Ion. — This is said to have remarkable 
effects on facial neuralgia; cases which have resisted many 
other methods of treatment have been reported cured by 
introduction of this ion into the affected area. Lewis Jones 1 
says about trigeminal perineuritis: "I have had a number 

1 British Med. Jour., August 31, 1912, p. 488. 



EFFECT OF IONS OX BACTERIA 247 

of complete successes in the treatment of this condition with 
salicylic ions, and in general the results are so good that prob- 
ably this has been the experience of all who have tried it." 
Leduc, 1 Dawson Turner, 2 and many others have published 
remarkable results in the treatment of neuralgia with sal- 
icylic ions. 

There are, no doubt, a number of ions which have not 
yet been tried which will be found therapeutically of great 
value, those already mentioned have been tested and their 
effects properly demonstrated. 

This method of treatment is within the reach of all prac- 
titioners, the apparatus which has already been described in 
other parts of this work in simple, inexpensive, and readily 
obtained; the technic is not nearly as difficult as many kinds 
of special work carried out by dentists. Thorough knowledge 
of the electrical phenomena applicable to electro-therapeutics 
is essential or the worker is liable to be puzzled by minor 
phases of the action of the current, which might interfere 
with persevering with the method, whereas when these are 
thoroughly understood, they are seen in their proper light and 
avoided or disregarded as of no vital importance. 

The Advantages of Ionic Medication. — The advantages 
of ionic medication in dentistry are many. It is easily 
carried out; it is not nearly as painful as many other opera- 
tions; it is effective; there are no ill effects; any discomfort 
caused at the time of administration disappears the instant 
the current is turned off; improvement is noticeable at once 
and is unmistakable by patient and operator; it places at 
our disposal a method of applying antiseptics, sedatives, 
stimulants, or styptics to a local area which act in concentra- 
tion on the part medicated. 

Effect of Ions on Bacteria. — The immediate effects of 
passing an antiseptic ion such as zinc, copper, silver, or 
iodine into an electrolyte, such as an area of periodontal 
tissue or a septic pulp canal, is the destruction of the micro- 
organisms contained in the area through which the elec- 

1 Arch. d'Elect. med., 1904. 

2 British Med. Jour., April 4, 1908. 



248 ELECTRO-THERAPEUTIC EFFECTS 

trically charged ions radiate. This effect has been clinically 
demonstrated by many eminent medical workers in this 
special branch of electro-therapeutics. The author has 
found that inflamed periodontal tissue, yielding pus from 
infected pyorrhea pockets, becomes perfectly healthy 
when treated with antiseptic ions. In addition to this, 
constitutional symptoms, which so often accompany this 
disease, such as general malaise, headache, indigestion, 
anemia, laryngitis, pharyngitis, aeneiform eruptions, and 
some forms of alimentary toxemia, subside and disappear 
altogether when they are caused (as they often are) by 
the absorption in the general circulation of the products 
of chronic suppurative conditions. It has been pointed 
out by exponents of vaccine therapy that the pus obtained 
from suppurating periodontal membrane contains a great 
variety of species of bacteria, that they are also found in the 
tissues of the affected area. Simms, 1 Goadby, 2 Eyre and 
Payne 3 have enumerated staphylococcus albus and aureus, 
streptococcus brevis and longus, micrococcus catarrhalis, 
spirilla and bacillus fusiformis and many other microorgan- 
isms but no specific organism. In administering vaccine 
prepared from organisms obtained from pyorrhea infection, 
the predominating organism or a mixture of organisms are 
employed with the hope of stimulating the production of 
antibodies (opsonins) of the corresponding variety to those 
responsible for the pathological condition existing and to 
render the patient immune by the injection of killed cultures 
of the suspected organism or organisms. 

It is with a certain amount of diffidence that the author 
ventures to make the suggestion (not having investigated 
the subject) that by the destruction of microorganisms 
in suppurative periodontal tissue, by ionization, the anti- 
bodies are provided by subsequent absorption of dead 
microorganisms into the general circulation. It is further 
obvious that if these microorganisms in the tissues are, 

1 Observations on the Bacteriology of Pyorrhea Alveolaris, Tr. Odont. 
Soc. Great Britain, 1907, xxxix, 164. 

2 Trans. Odont. Soc. Great Britain, xxxvii, 145. 

3 Proc. Royal Soc. Med. (Odont. Sect.), December, 1909. 



EFFECT OF IONS ON BACTERIA 249 

in their active state, responsible for the general systemic 
disorders accompanying the disease, the right organisms 
will always be provided; there will be no mistake on that 
point. The question arises whether the numbers of living 
bacteria to be found in the tissues and destroyed there by 
the ionic treatment are sufficiently large to affect the opsonic 
index. 

However this may be, it is a fact that constitutional 
disorders which have arisen from the effects of existing 
chronic pyorrhea alveolaris usually disappear when the 
disease has been treated by ionic medication, and locally 
the tissues are restored to normal condition. Malaise will 
nearly always disappear before the disease can be said to be 
cured. This is a frequent experience of the writer in cases 
which have come under his notice. 

It has been demonstrated experimentally by Breuer and 
Zierler, Lehmann, and others that the passing of a current 
alone has a sterilizing effect on cultures of bacteria in agar, 
and Zierler reports having put this into practice for steriliz- 
ing root canals, using small current of 3 or 4 milliamperes, 
with satisfactory results. 

Bethel has also shown that microorganisms infecting pulp 
canals can be destroyed by passing a current with nitrate 
of silver as the solution electrode, in which he doubtless 
obtained silver ions, but he attributes the effect to a com- 
bination of electrolysis and cataphoresis. 

Hoffendahl also published similar effects on bacteria in 
the treatment of root canals with the current. 

Josef Peter 1 has published his clinical experience in the 
same direction with the current and states that "the result 
was excellent in every case." 

The author has used ions of zinc, silver, copper, or iodine 
for a number of years; he rarely fills a pulp canal without 
subjecting it to ionic treatment. Ions of zinc seem to be 
the most effective, a perfect sterilization of the canal walls is 
effected and septic disturbances after filling of the roots is 
practically impossible if this operation is carried out with 
due care. 

1 Dental Cosmos, vol. xlvii, p. 1136. 



CHAPTER XL 

TECHNIC OF IONIC MEDICATION IN DENTAL 
OPERATIONS. 

When a continuous current from the main is used, the 
chair in which the patient is seated must be insulated from 
all contact with earth. Most dental chairs have a large 
amount of metal about them, and if they rest on wooden or 
even carpeted floors fairly good contact with earth may be 
established, especially in very damp weather. A perfect 
insulation is effected by resting the metallic base of the chair 
on a rubber mat. 

Water pipes or gas fixtures should not be within reach 
of, or be touched by, either patient or operator when the 
current is being used. 

Metallic supports for cuspidors must not be touched if in 
contact with earth. 

Saliva ejector must not be used with the patient in elec- 
trical contact; there is only a slight chance of contact with 
earth being established in this way, but it is best not to 
take the chance. 

A continuous current either from a switchboard described 
(p. 95) or from a voltaic cell battery (p. 94) is the proper 
current for ionic medication. 

The current at the starting point (zero) should be less 
than 0.1 milliampere. It must be so regulated by resistance 
in circuit that it can be increased in E. M. F. and in current 
strength by not more than 0.1 volt and 0.1 milliampere at 
a time. Current collectors which switch on one cell at a 
time increased the voltage and amperage too suddenly and 
should not be used for ionization of oral tissues. 



IONIC MEDICATION IN DEXTAL OPERATIONS 251 

.1 mill [amperemeter is essential. 

Conducting cords should be perfect and attached securely 
to the switchboard or battery terminals and to the electrodes; 
loose moving contacts produce disagreeable little shocks by 
occasional break of current. 

The active electrode (p. 109) must be selected to suit the 
particular purpose for which ions are required. 

In pyorrhea treatment metals corresponding to the solution 
employed or else of platinum must be used; platinum may be 
used with any solution, as it is not soluble itself. The area 
and cross-section of an active electrode influences the 
density of the current. Very fine electrodes are painful 
in periodontal tissue even with a small current; an electrode 
of 2 mm. x 1 mm. x -1 cm. tapering to the required size, 
just large enough to be admitted easily into the spaces of 
pockets to be medicated, should be used. 

The solutions should be conveyed to the site of medication 
on absorbent wool tightly wound about the blade of the 
metallic electrode conductor, and wetted occasionally, as 
replenishing becomes necessary. 

The electrode should be placed in position before raising 
the current from zero, the current should then be gradually 
increased until 2 to 5 ma. are registered and the patient 
indicates that a pricking sensation is felt in the tissues; 
it should then be reduced by 0.2 ma. and the electrode kept 
steadily in position for from one to five minutes according 
to the necessity for a large or small dose of ions. It should 
be the object to use as high a current strength as possible 
up to 15 ma. without giving undue pain. 

The soft tissues are less sensitive to current than dentine 
at necks of teeth, the metal electrode should be kept away 
from sensitive teeth as much as possible. Intervals of 
treatment in pyorrhea alveolaris should be three times 
a week for first week, twice a week for second and third 
weeks, once a week after; this should be varied according 
to the severity of the case, it being best to vigorously keep 
up treatment at first until all pus disappears. 

Metallic fillings in live teeth should be avoided when 



252 IONIC MEDICATION IN DENTAL OPERATIONS 

possible. When impossible, small currents for a longer time 
should be used. 

The current should be reduced to zero before removing 
the electrode from site of ionization or a painful shock will 
be experienced. 

The shaft of active electrode should be insulated or not 
allowed to touch the cheek, lips, or tongue. 

The saliva should be kept away by cotton rolls or napkins. 

The indifferent electrode should be strapped to the patient's 
wrist or held by the patient or placed under the chin. It 
should always be covered with several layers of lint and 
should be moistened with water or a saline solution. If 
the metallic indifferent electrode causes blisters or smarts 
the skin, a carbon electrode in a glass dish of tepid water 
with a little chloride of sodium in it should be used. The 
carbon should be covered with lint and the patient's hand 
pressed firmly on it. (See page 109, Fig. 46.) 

Rings should be removed from the hand holding indif- 
ferent electrode. 

Electrodes should be held firmly and contact over as 
large an area as possible insured. 

The poles should be tested in all new switchboards or 
batteries (see p. 42). 

When acid radical ions are required, a lower current 
strength will be indicated, as the negative pole is more 
painful with small electrodes than the positive. 

It is best to begin with a low voltage and current strength, 
as it will be found that the resistance of the body becomes 
less as the seance goes on, and highly susceptible patients 
will stand more if this precaution is observed. 

The principles peculiar to the movement of ions referred to 
on p. 233 must be observed. 

For anesthesia of dentine or pulp active electrodes of 
as large an area as possible must be used. The metal 
conductor must not be brought in contact with the dentine 
or pulp; cotton-wool saturated with the anesthetic should 
first be placed in the cavity and the electrode pressed firmly 
on this. The area of the electrode can be increased by 



IONIC MEDICATION IN DENTAL OPERATIONS 253 

placing a piece of platinum foil over the wool and attaching 
the electrode to this. 

Resistance in dentine is great, therefore the E. M. F. 
required will be great, and current strength required much 
less than in dealing with soft, moist tissue; 0.5 ma. will 
sometimes be painful but this amount of current is often 
sufficient to anesthetize dentine, or it may be raised to 1 or 
2 ma. after a few minutes' seance. When the pulp becomes 
anesthetized a current of 3 or 4 ma. will give no sensation, 
and this is a sign that the pulp may be drilled into without 
pain. 

For sterilizing pulp canals, the electrode of fine iridio- 
platinum wire should be passed into the canal or canals, a 
solution of antiseptic to be used must be introduced into 
the cavity on cotton-wool, and the canal flooded with it. 
Current strength and time required to sterilize the canal must 
be in direct ratio: if 2 ma., 15 minutes; if 3 ma., 12 minutes; 
if 4 ma., 8 minutes; if 5 ma., 5 minutes; this is approximately 
a good working basis. 

For treatment of fistulous tracts, a soluble copper electrode 
should be passed into the fistula and to this, in situ, a 
platinum or copper active electrode connected. A current 
of 3 to 5 ma. is usually bearable. Five minutes will furnish 
a dose of copper ions sufficient to sterilize the tract. The 
pulp canal should be sterilized also as above described. 
The soft tissues will adhere firmly to the electrode ; it should 
not be forcibly removed, the tissues will relax their hold 
in a short while, and if not, reverse the poles and pass a 
negative current for about half a minute, this will loosen 
the electrode. 

For bleaching discolored teeth a platinum electrode should 
be used and the patient can hold the indifferent electrode, 
or the more effective method is to place the two electrodes 
of platinum wire in the tooth, separated there by as far a 
space as circumstances will allow and interpose cotton-wool 
saturated with the bleaching compound in solution. 

Care must be taken not to short circuit the current either 
within the tooth or without by allowing electrodes or wires to 



254 IONIC MEDICATION IN DENTAL OPERATIONS 

meet. By this method with fine electrodes 5 ma. current 
produce some heat, 10 to 15 ma. produce intolerable heat in 
the tooth when the bleaching material becomes dry. 

The tooth should be isolated by applying rubber dam. 
Metallic fillings should be removed. Fine platinum wire 
electrodes produce more heat than thick wires. The poles 
should be reversed with the electrode in situ, when the 
operation is about half completed. 



CHAPTER XII. 
HIGH-FREQUENCY AND STATIC CURRENTS. 

X-ray and High-frequency Currents. 

These currents are much used in medical electricity 
for general electrification of the body, and for local appli- 
cation. The effects are of a mixed character, acting largely 
on the nervous system, circulation, respiration, and as 
d'Arsonval has shown, on microorganisms. 

Therapeutically these currents are applied in many 
special ways for treatment of diabetes, gout, rheumatism, 
tuberculous glands, neuralgia, pyorrhea, and many other 
local and general diseases. Mr. L. C. Creasy 1 advocates a 
special form of static application for treatment of glands 
which are enlarged by the absorption of toxins from the 
teeth — lymphadenitis. This he terms Intensive Irradiation 
and Static Wave Treatment. The treatment consists in 
first treating the affected area by intensive irradiation from 
a 500 candle-power incandescent lamp with special reflecting 
properties, this increases local metabolism and elimination. 
The static wave current is then applied with the object of 
increasing physiological resisting power of the parts. "Pas- 
sive congestions are removed by improving the physiological 
'tone' of the affected region." 

This method of applying the static wave current is best 
described by quoting the words from that author who 
quotes Potts: "The patient, on an insulated platform, 
must be connected to the side of the static machine that 
is not grounded. The electrodes should be of pliable metal 
and the treatment should be commenced with the prime 

1 The Practitioner's Encyclopedia of Medicine and Surgery. 



256 HIGH-FREQUENCY AND STATIC CURRENTS 

conductors practically closed. On drawing the prime con- 
ductors apart the wave current will become apparent and 
as wide a spark should be used as can be easily tolerated 
by the patient." 

This form of treatment for glands affected by toxins 
from teeth or gums is a distinct advance on anything so 
far recommended outside of surgical treatment for acute 
and chronic lymphadenitis. 

Much controversy has arisen as to how these glands are 
affected, and as to the correct diagnosis of lymphadenitis, 
but outside of aseptic oral treatment nothing seems to have 
been recommended for treatment in chronic cases. 

High-frequency currents have attracted little attention. 
They have, however, been used on the Continent with 
considerable success in the treatment of acute periodontal 
disease. It is claimed that this oscillating current has an 
ionic effect on solution electrodes placed on the tissues. 

Dr. William Dunn, of Florence, has pointed out that 
high-frequency currents possess valuable therapeutic prop- 
erties which are singularly adapted to the treatment of 
pyorrhea alveolaris. He points out that the stimulating, 
antiseptic, and antitoxic properties of high-frequency currents 
are especially indicated in the treatment of diseased tissues 
in which the pathological conditions are accompanied with 
depressed or lost vitality or with a disturbance of metabolic 
functions. Together with his colleague, Dr. Luigi Arnone, 
of Florence, good results are claimed from high-frequency 
treatment of pyorrhea, using the currents as an auxiliary after 
surgical treatment of the disease, he says, " In every case with 
marked beneficial effects, the gums toning up and looking 
healthy and hard in a short time, pus ceasing more rapidly 
than before, and the teeth bracing up rapidly." Dr. Dunn 
also puts forward the anesthetic effects of high-frequency 
currents in dental treatment, pointing out the great usefulness 
of this property of these currents in cases where cocaine is 
contra-indicated, he says, "sufficient anesthesia has been 
obtained locally to perform painlessly some of the minor 
operations, such as lancing gums, removing roots, etc." 



X-RAY AND HIGH-FREQUENCY CURRENTS 257 

Other workers in this special electrical branch have reported 
successful anesthetic effects from high-frequency currents, 
among them Dr. Didabury claims a high degree of success. 

A form of high-frequency treatment which is called by 
the author, Monsieur F. Morel, 1 of Dreux, "alto-frequent 
effluvation," has been described by him as having remark- 
able effects in the treatment of pyorrhea alveolaris by the 
formation of what he terms "mixions." In the following 
description of the action of these currents he says: "This 
effluvolysis does not, like electrolysis, have for its result 
a simple transport of the ions which travel respectively 
toward the positive or the negative pole, but there is produced 
in consequence of the frequent periods, molecular vibrations 
to which these periods give rise — vibrations which constitute 
a veritable ionic bombardment. It is no longer a question 
merely of cathions or anions; all these ions clash together, 
mix, unite, and combine to form new molecules of a different 
chemical formula from the primitive element. The exchange 
of the ions is cathodic and anodic at the same time at the 
point of application of the effluves ; I will call the molecules 
thus newly formed 'mixions.' " 

Monsieur Morel states that he has experimentally intro- 
duced ions into the bodies of animals by this method of 
alto-frequent effluvation and produced in them therapeutic 
effects characteristic of the ion used, cyanide of potassium 
and oxalate of strychnine producing convulsions and death 
to guinea-pigs. 

Reading the action of the ions formed by the effluvolysis 
of bichromate of potash he gives the following formula : 

Cr CrO 

Cr20?K2 + 4H2O = anions — + cathions — = mixions HO 

H lv KOH 

which shows that the chemical composition of the bichro- 
mate of potash and water is changed by the effluvolytic ioni- 
zation into chromic acid (2Cr0 2 ) + caustic potash (2KOH) 
+ water (H 2 0), and for them he claims antiseptic and 

1 Bulletin du Syndicat des Chirurgien-Dentistes de France. 
17 



258 HIGH-FREQUENCY AND STATIC CURRENTS 

stimulating effects from the chromic acid, and solvent prop- 
erties on tartar for the caustic potash. The effect he claims 
is a perfect medication of "mixions" which are not eliminated 
from the tissues for some days; he states that "urologic 
analysis does not reveal to us the presence of the medicament 
until twelve hours after efnuvation, and does not become 
eliminated before the end of two days. 

In addition to the antiseptic effect of the ions, a stimu- 
lating effect in the protoplasm of cells is produced and a 
further antiseptic effect from the production of ozone at 
the contact of the electrode. 

The technic of this method of treatment "is briefly as 
follows : 

The gums or necks of affected teeth are painted with a 
solution of 

Fluosilicate of soda 2 gm. 

Chloride of ammonia 1 " 

Chloride of potassium 11 " 

Salicylate of theobromine 1 " 

Methylal 50 cgm. 

Distilled water 20 gm. 

Filter. 

A pad of cotton-wool saturated with a solution of bichro- 
mate of potash in water 1 to 10 is placed over the necks 
of 4 teeth at a time and on this pad is placed the empty 
electrode of the alto-frequent current; this is pressed firmly 
but not roughly into place, and an "alto-frequent rain of 
effluves" is passed into the tissues. 

In advanced pyorrhea cases a metallic electrode is used 
which projects about ten sparks in the infected pockets. The 
operation of effluvation lasts for five minutes at a time and 
three such are given ; this is repeated every two days for six 
visits. Metal fillings must be insulated by covering them with 
gutta-percha, to protect against pain which the current 
would otherwise cause. 

X-rays and High-frequency Currents. — From time to time 
reports have been made in the journals of the good results 
obtained by the combined use of .r-rays and high-frequency 



X-RAY AND HIGH-FREQUENCY CURRENTS 259 

currents in the treatment of pyorrhea alveolaris. Dr. 
C. H. Parker, 1 of Chicago, in 1903, advocated the use of 
.r-rays for one or two minutes and then high-frequency for 
five minutes, having previously sprayed the affected gums 
with a mixture of iodine, aconite, myrrh, and wintergreen. 
He says : " The object of spraying the gums with medicament 
before turning on the x-ray and high-frequency currents 
on the patients is to have the chemicals carried into the 
tissues by these currents." His method of applying the 
high-frequency electrodes over the mouth of the patients 
also has the effect of saturating the tissues with ozone 
which by its high oxidation properties increases metab- 
olism and elimination with consequent improvement in the 
condition of stasis which attends the disease. From this 
method of treatment very good results were obtained. 

Dr. F. LeRoy Satterlee, Jr., 2 of New York, improved 
on the method of applying the high-frequency currents to 
pyorrhea teeth by applying the vacuum electrode directly 
to the gums, and agrees with Dr. Parker on the results 
obtained by this treatment, he says: "This treatment in 
combination with .r-rays has proved very successful in a 
number of cases, and in the early stages of pyorrhea where 
the alveolus has not been entirely sloughed away we may 
claim a complete cure, the teeth tighten up, with restoration 
of the gums to a healthy condition." Two years later Dr. 
Le Roy Satterlee, 3 after further testing the use of .r-ray and 
high-frequency currents in the treatment of pyorrhea, says: 
"I have derived the best results from a combination treat- 
ment of x-rays and the use of special vacuum electrode of my 
own design that conveys the high-frequency currents and at 
the same time bathes the gums and underlying tissues in the 
rich radiations of the bi-ultra-violet rays. A metal electrode 
is meanwhile held in the hand to complete the circuit through 
the body of the d'Arsonval currents." 

S. Tousey, 4 of New York, advocates a combination of 

1 Dental Cosmos, xlv, 947. 

2 Ibid., xlvi, 642. 3 Ibid>) x i viii) 274. 
4 Medical Electricity and Rontgen Rays, p. 569. 



260 HIGH-FREQUENCY AND STATIC CURRENTS 

x-ray and high-frequency currents for the treatment of 
pyorrhea alveolaris. A specially prepared x-ray tube with 
the rays localized to an opening in a shield of 2\ inches is 
used. "The rays should be about No. 4 of the Walter or 
of the Benoist scale, the resistance equal to a parallel spark 
of about 2 inches, the primary current about 3 amperes, with 
a 12-inch coil and Wehnelf interrupter and a current of 2 ma. 
passing through the x-ray tube. The anticathode of the 
tube is about 10 inches from the face, the lips are open, 
exposing the teeth and gums, and the time of exposure is from 
one to two minutes." The x-rays escape only from this 




Fig. 144. — Tousey's x-ray tube for treating pyorrhea. 



special tube at the end of the prolongation and the strength 
of application is much reduced as compared with the ordinary 
x-ray tube. Treatments are given to the affected gums twice 
a week, immediately followed on each occasion by high-fre- 
quency currents, applied by vacuum electrodes especially 
prepared for this purpose, which fit the different aspects of the 
alveolar border and necks of the teeth. The high-frequency 
is applied for thirty seconds to one place and then moved 
to another. The usual ozone effect is noticed about the 
electrode and the application is said to be entirely painless. 

Tousey says: "The results are very prompt relief of pain 
and improvement on the ulceration, so that in three weeks 



X-RAY AND HIGH-FREQUENCY CURRENTS 261 

the dentist almost always reports that the teeth are better 
than for six months previously. The teeth gradually tighten 
up and the tenderness disappears." 

He recognizes that there are many forms of pyorrhea 
and that the best results are not obtainable in some forms 
of the disease by this combined x-ray and high-frequency 
method. Those cases which are dependent on constitu- 
tional complications would be contra-indicated. It must, 
however, be kept in mind that the x-rays are very destruc- 
tive rays to tissues and too long exposure might result in 
burns, even with as low a current as here recommended. 
The danger to which the operator is constantly exposed 
must also be remembered, and special attention is drawn to 
this in dealing with the technic of Dental Radiography in 
another chapter of this work (p. 148). 



CHAPTER XIII. 
ELECTRO-THERAPEUTICS IN DENTISTRY. 

Treatment of Root Canals — Periodontitis from Septic Pulp — Acute 
Local Periodontitis — Alveolar Abscess — Trismus from Impacted Third 
Molar — Chronic Alveolar Abscess — -Perforation of the Root — Necrosis of 
the Jaws — Marginal Gingivitis. 

Treatment of Root Canals. — The sterilization of root canals 
which have become septic by death and decomposition of 
the pulp, in which microorganisms infect not only the canals 
but also the tubuli of dentine, is by no means an easy matter 
to accomplish, as may be deduced from current literature on 
the subject, in which therapeutic agencies of the most 
powerful antiseptic type have been recommended from time 
to time, only to be rejected after trials, when it is found that 
secondary manifestations of septic infection occur in spite of 
their use. This experience is due to the osmotic method of 
application, by which the sterilizer does not reach deep- 
seated bacteria in the tubuli or apical foramen. Sterilization 
by ionic medication overcomes this difficulty by the migra- 
tion of ions into the tubuli and along the most tortuous or 
constricted root canal to the apex, as can be experimentally 
demonstrated by the following experiment. 

Take a freshly extracted tooth, cleanse the root canal of 
all debris of pulp, fill the pulp chamber and canal with 5 
per cent, solution of ferrous sulphates, insert a fine, smooth, 
steel nerve instrument into the canal as far as it will go 
toward the apex, insert the tooth up to the neck in a small 
sponge in a porcelain dish containing tap water. To the 
nerve instrument in the canal connect the positive pole of the 
generator and to the sponge connect the negative pole. Turn 
on the current and allow 5 ma. to pass for 5 minutes. Turn 
off the current, remove the instrument and wash out the canal 



TREATMENT OF ROOT CAXALS 263 

thoroughly with tap water, saw through the root trans- 
versely, and plaee the sections in 10 per cent, solution of 
ferricyanide of potassium for four hour-. The canal to the 
apex and the tubuli will he seen stained Prussian blue: sec- 
tions cut transversely across the root will demonstrate that 
ferrous ions, which are colored blue, have penetrated a con- 
siderable distance into the tubuli in the case of a young 
subject to the very ends . This demonstrates that by 
passing a continuous current for a given time the conducting 
ions of a metallic salt are transported by the laws of con- 
duction into the tubuli of dentine and through the apical 
foramen into the surrounding tissue. The depth of pene- 
tration will in some measure depend on the organic matter 
in the tubuli and the size of the opening at the foramen, as 
well as the current strength available. 

The electrolytic dissociation and migration of ions has 
been explained, and it has been shown that the ions are the 
conductors of current. This theory when applied to the 
electrolytic sterilization of root canals is dependent for its 
success on two factors: (1) The employment of adequate 
current strength or energy to dissociate a sufficient dose of 
ions from the electrolyte used in a given time: the time must 
be calculated in direct ratio to the current strength. If 
only 2 ma. current is tolerated by the patient, fifteen minutes 
will be required: if 3 ma.. 12 minutes: if 4 ma.. S minutes: if 
5 ma.. 5 minutes. For practical purposes this ratio provides 
a working basis, which is desirable in electrical treatment. 
(2) The employment of an electrolyte, which when dissociated 
by the current, the conducting ions are of an antiseptic nature. 
This is an all-important factor, which can be determined by 
experimental and clinical evidence, the latter must be based 
on actual experience extending over a considerable time and 
not only from a dental but also medical stand-point. Suffi- 
cient clinical evidence has been recorded to place ions of zinc. 
copper, silver and mercury in the category of highly antiseptic 
ions, as has been already referred to see pp. 234 and 244 from 
a medical and dental aspect. For root sterilization the author 
has had most success with zinc and silver ions. 



264 ELECTRO-THERAPEUTICS IN DENTISTRY 

Recently Prinz 1 has propounded the theory that zinc ions 
have no germicidal properties and claims that for root 
sterilization chlorine ions from chloride of sodium is more 
effective than any of the above salts, and quotes various 
experiments as evidence. He says "zinc ions are devoid of 
supposed germicidal properties" but gives no data of his 
experience with this ion from a clinical stand-point, probably 
having had none. E. Zierler (1905) first brought forward the 
claim that sodium chloride solution electrolytically applied 
sterilizes root canals. Both these authors disregard the 
principles of ionic medication by dissociating sodium ions or 
chlorine at the anode and relying on the anion chlorine which 
does not move away from the positive pole but is simply 
eliminated, it therefore does not penetrate the dental tubuli 
to any depth, it is the sodium (kathion) which is conducted 
by the current in passing. It is therefore highly improbable 
that the full sterilizing properties of chlorine are available 
with this technic, sterilization being only possible on a very 
superficial area of the wall of the root canal so treated. 

The operation of electrolytic sterilization of root canals is 
briefly as follows: The patient is seated in an insulated 
chair; the tooth to be treated is cleansed from all debris of 
dead pulp, the opening to the pulp chamber being freely 
enlarged to admit of electrolyte and electrode. The canal 
should be enlarged a short way to admit the electrode and 
care taken that debris of inorganic matter does not make an 
obstructing plug to the passing of current through the 
length of the canal. The tooth must be kept free from 
moisture from the mouth by rubber dam during ionization 
and after until the cavity is sealed. The root canal should 
be flooded with 3 per cent, zinc chloride and a fine iridio- 
platinum electrode inserted as far as it will go toward the 
apex, but not through the apex. The electrode should be 
securely attached to an insulated hand-piece and connected 
with the positive pole. The patient should hold the indiffer- 
ent electrode, which should be of large size and covered with 

1 Dental Cosmos, April, 1917, p. 388. 



TREATMENT OF ROOT CAXALS 



265 



several layers of lint moistened with saline solution. The 
current should be at zero and not turned on until the 
electrodes are firmly in position, the rheostat resistance 
should then be gradually and slowly released, and the patient 
instructed to indicate when the current is felt in the tooth by 
raising the hand; this may occur at 2 or 3 ma., when it should 
be reduced y 7 ma., and kept at this for half a minute when 
usually it can be increased about 1 ma., or if greater current 
strength is tolerated it should be taken advantage of. The 
time is then noted and sterilization effect judged in direct 
ratio of time to the current strength in use, according to the 
working basis given already. 




Fig. 145. — Premolar with electrodes in position for ionization of roots. 



A two- or three-rooted tooth can be treated at one time by 
inserting wire electrodes into each canal and connecting them 
together securely (see Fig. 145). When sterilization has been 
completed the current should be reduced to zero and the 
electrodes removed, a dressing of cotton-wool saturated with 
the zinc chloride solution should be inserted into the canals 
and the cavity carefully sealed with gutta-percha. This 
dressing should remain for two or three days when the canal 
can be filled after again sterilizing it as before, as a pre- 
cautionary measure, especially is this second dose of ions 
indicated if there is any evidence that at any previous time 
periodontal inflammation has existed. 



266 ELECTRO-THERAPEUTICS IN DENTISTRY 

Periodontitis from Septic Pulp. — The complication of perio- 
dontitis following the death of the pulp, indicating that septic 
infection has passed through the apical foramen, requires 
great care in obtaining a sterile root to prevent recurrence 
of periodontal inflammation. The decomposed pulp tissue 
should be removed as thoroughly as the tender tooth will 
allow and the canals electrolytically sterilized at the first 
treatment as thoroughly as possible without resorting to 
rubber dam or the use of drills in the inflamed condition, an 
antiseptic dressing lightly inserted and the cavity sealed with 
varnish wool for twenty-four hours. At the end of this time, 
or when the inflammation has subsided sufficiently, the 
canals should be enlarged and thoroughly cleansed; zinc 
ions should be introduced with the same technic as de- 
scribed for treatment of root canals, the canals and cavity 
sealed in the same way, and the patient dismissed for a week, 
at the end of which time if every sign of inflammation has 
disappeared, the root should be again sterilized with zinc 
ions and filled permanently, or if not quite free from inflam- 
mation it should be filled temporarily, and the patient dis- 
missed for a few days, when it should be finally sterilized 
and filled. 

Silver ions electrolytically dissociated from a 2 per cent, 
solution of nitrate of silver are also effective for sterilizing 
septic roots of this kind, but on account of the staining prop- 
erties of this preparation its use must be confined to back 
teeth. 

The most favorable cases are those with large canals or 
canals which are easily enlarged to the apex, which admit an 
electrode to the end of the root. Ions pass readily through 
these and sterilize the tissue, destroying bacteria which have 
infected them and caused the inflammation. 

A case typical of the effect of electrolytic sterilization may 
be cited. A patient, the brother of a dentist in America, had 
acute periodontitis in a lower premolar which was filled 
temporarily. This tooth, the patient informed me, could not 
be permanently filled because he " so often had to have the 
root treated." The filling and root filling were readily 



ACUTE LOCAL PERIODONTITIS 267 

removed, and the root was electrolytically sterilized with zinc 
ions, with 4 ma. current strength for eight minutes. The 
inflammation subsided that day, and two days later it was 
again sterilized in the same manner and the root canal and 
cavity filled. This treatment effected a permanent cure of 
the trouble. The root has now been filled for five years with- 
out recurrence of inflammation. The patient's brother wrote 
me for information of this method of treatment, saying a 
cure had been effected in one of the most troublesome cases 
he had ever had to deal with. 

Acute Local Periodontitis. — This condition is due to septic 
extension from the pulp and is the continuation of perio- 
dontitis just described, which terminates in suppuration and 
formation of alveolar abscess. If the abscess has not attained 
large dimensions and the apical foramen will admit of evacua- 
tion of pus through the root canal, successful and rapid 
termination of the abscess can be carried out by electrolytic 
sterilization as follows: First syringe the canal to remove 
all septic matter and evacuate all pus and blood available, 
then flood the canal with 3 per cent, zinc chloride and insert 
a few shreds of cotton-wool soaked with the solution to hold 
the supply of solution in the canal. Pass a fine iridio-platinum 
electrode to the apex of the canal and perform electrolytic 
sterilization in the same manner as described in the foregoing 
treatment for periodontitis. A large dose of zinc ions will be 
required, and it is advisable to extend the time, in proportion 
to current strength rule, to a couple of minutes longer than 
for ordinary root sterilization. In this way zinc ions are 
introduced into the abscess area, and will often terminate an 
abscess in less time than the ordinary method of sealing anti- 
septics in the root canal. After the first treatment a cotton 
dressing with some antiseptic oil, like dentalone or oil of 
cloves should be inserted until the next day, when this should 
be removed and the canal thoroughly syringed and cleansed 
with nerve instruments with the object of evacuating any pus 
or blood that might remain, and also removing all the essential 
oil present. The sterilization should again be carried out as 
before. 



268 ELECTRO-THERAPEUTICS IN DENTISTRY 

In addition to this the inflamed area immediately over the 
root of the tooth should be treated by applying a weak 
aqueous solution of tincture of iodine (one part tincture and 
ten water) on cotton-wool and pressing it into position with a 
flat platinum electrode 3 or 4 mm. wide, then reverse the 
polarity and ionize the application with the negative pole, 
the patient holding the positive pole. It will be noted that 
the iodine will be bleached white as the process of driving the 
ions into the tissue proceeds. The time required to do this 
will be five to eight minutes, according to the amount of 
iodine liquid contained on the wool. This treatment of the 
surface area with iodine ions should be repeated when 
sterilizing the canal and abscess as long as the inflammatory 
symptoms are present. 

Referring to this method of treatment of the surface area 
over the root Dr. J. M. Fogg, 1 of Philadelphia, states that the 
current has been to him of greater value than in any other 
class of cases, and that "in most cases one application is all 
that is necessary to reduce the inflammation, the pain 
quickly subsides, and there is seldom a recurrence of the 
disorder." The author has also found that this external 
treatment in abscess cases is a great help and relieves the pain 
effectively. 

Alveolar Abscess. — When an acute abscess at the apex 
extends through the bone into the overlaying soft tissues, 
treatment through the root canal is obviously impractical 
and the usual course of lancing and evacuating the pus must 
be resorted to. The healing of the abscess can be greatly 
facilitated after evacuating the pus by syringing through the 
opening in the soft tissue with warm 2 per cent, solution of 
zinc chloride, filling the abscess with the solution and intro- 
ducing a zinc probe electrode into the area, attached to the 
positive pole, the patient holding the negative electrode; a 
current of 3 or 4 ma. can usually be tolerated, and five minutes' 
ionization of the abscess area will sterilize the parts and 
assist greatly in relieving the condition. In addition, as 

1 Dental Cosmos, xli, 27. 



TRISMUS FROM IMPACTED THIRD MOLAR 269 

soon as it is possible to treat the root canals, electro- 
sterilization should be carried out as described previously for 
periodontitis, and the root filled with the same technic. This 
treatment is effective in preventing the subsequent develop- 
ment of a fistulous tract or a chronic abscess sac. 

In cases of mandibular teeth affected by alveolar abscess, 
which threatens to gravitate to the outer surface of the jaw 
ionic medication is specially indicated to furnish a lasting and 
effective antiseptic dressing, and a means of arresting the 
progress of breaking down of the soft tissues. 

Trismus from Impacted Third Molar. — Abnormally placed 
or impacted mandibular third molar frequently causes infec- 
tion of the soft tissues surrounding the crown, by the for- 
mation of a pouch or pocket, into which debris of food 
collects and decomposes, resulting in ulceration and slough- 
ing of tags of gum, extensive inflammation and condition 
of trismus occurs. The writer has found ionic medication 
in these cases of the greatest value, particularly in reliev- 
ing trismus, which appears to be caused more from a reflex 
action of the nervous system, than from inflammation of 
the muscles. The limitation of movement of the mandible 
can be invariably relieved as follows: Syringe the affected 
area to remove loose debris of food and pus, then wrap a 
zinc electrode with cotton-wool, and saturate it with 3 
per cent, chloride, pass the point of the electrode to the 
bottom of the pocket or under the flap of gum, so as to 
medicate the ulcerated area, pass 3 to 5 ma. current from the 
positive pole for five minutes. If the space available between 
the teeth is insufficient to admit the electrode, a well-curved 
electrode can be passed between the cheek and the teeth 
into the pocket or space, but as the cheek is likely to touch 
the electrode and increase its conducting area, a larger current 
will be required to sterilize the affected part, 5 or 6 ma. for 
five minutes will often be tolerated, and is advisable. This 
will relieve the trismus considerably in twenty-four hours, 
and by repeating the treatment daily, with frequent use of an 
antiseptic mouth wash, the inflammation will subside, and the 
trismus be reduced to such an extent that in a few days it is 



270 ELECTRO-THERAPEUTICS IN DENTISTRY 

often possible to operate for the permanent relief of the 
condition. 

A case in point recently under treatment is typical and 
lends itself in support of the writer's conviction that these 
cases of trismus are entirely due to nerve reflex, either directly 
by the influence of the inflammatory irritant on the vaso- 
neural circuit or indirectly by absorption of toxic products, 
or a combination of both these. A medical practitioner 
brought a young lady in consultation for what he suspected 
might be pyorrhea. Glands of the neck on the right side had 




Fig. 146. — Impacted third molar. 

been operated on twice, and another operation was impending; 
temperature was 100° to 101° at night; exceedingly nervous ; 
very foul breath ; teeth decayed in several parts of the mouth 
and hypersensitive; very marked trismus which had existed 
for six months during which time limitation of movement had 
varied considerably; at this time a forefinger could just be 
passed between the front teeth, the angle of the jaw on right 
side enlarged. A large septic pocket existed behind the second 
mandibular molar through which the crown of the third molar 
could be felt with a probe. Radiograph showed the third 



CHRONIC ALVEOLAR ABSCESS 271 

molar placed horizontally against the crown of the second 
molar. (See Fig. 146). 

Treatment by ionic medication with zinc ions, as described 
already, improved the condition of trismus in five days, so 
that it was possible to clean up the mouth generally; the 
temperature became normal in two days after the first treat- 
ment, in seven days inflammation had almost subsided, and 
the mouth could be opened sufficiently to easily admit the 
forceps when the second molar was extracted. The nervous 
affection subsided, the glands got normal. Relieving of the 
trismus in this case was of the greatest value in bringing 
about a rapid cure of what might have been a prolonged and 
distressing condition. 

Chronic Alveolar Abscess. — Chronic alveolar abscess in 
which a fistulous tract is formed from the root of the tooth, 
opening on the gum, with suppuration constantly or at 
intervals, is frequently seen in the mouth, and is often difficult 
to cure. The condition is usually caused by septic infection 
of the pulp canal which supplies toxins and keeps up the 
suppurative process. 

Treatment by electro-sterilization consists in opening the 
pulp canal to the apex and filling the canal with 3 per cent, 
zinc chloride or 2 per cent, silver nitrate, then with a little 
cotton-wool to retain the solution in the canal, pass a fine 
iridio-platinum electrode to the apex and pass 3 to 5 ma. 
current from the positive pole for five to twelve minutes, 
according to current in use, reduce the current to zero and 
seal the canal temporarily with dentalone on cotton and a 
tight gutta-percha filling in the crown cavity. Pass a copper 
probe through the opening on the gums the length of the 
tract till it reaches the root of the tooth, attach the positive 
pole to this and pass 3 ma. current for eight minutes; a 
useful size probe is thick copper bell wire and a small hollow 
coil can be made at one end to receive and steady the hand 
electrode by winding the wire around the shaft of a steel 
excavator (see Fig. 49) . On turning off the current the tissues 
will be found to adhere to the probe, this can be released 
at once by reversing the poles and passing 1 ma. for one 



272 ELECTRO-THERAPEUTICS IN DENTISTRY 

minute, or by waiting a few minutes the contracted tissue 
will release its hold. The tract will be stained green from 
cupric ions imparted. These ions, which are highly antiseptic, 
are due to a secondary reaction, which takes place about the 
soluble electrode, the result of electrolytic solution pressure 
on the copper with the tissues as the electrolyte. 

Often a single treatment of root canal and gums by this 
electro-sterilization method will permanently cure a chronic 
abscess, but before filling the root canal permanently it is 
best to test the efficacy of the medication by waiting a 
week, and then sterilizing the canal again before filling it, or 
in case the tract still discharges to do both again and wait 
another week. 

If the sinus extends to the skin on the outside of the face 
and it is desired to save the tooth, the process of electro- 
sterilization of root canal with zinc ions and the tract with 
copper ions as already described can be effectively done. 
These cases may be accompanied by cicatricial adhesion of 
the sinus by a fibrous cord to the surface of the bone, resulting 
in an ugly scar. Lewis Jones, 1 Leduc and others have pointed 
out the sclerolytic action of the current with chlorine ions, 
and while it does not seem certain whether the chlorine 
ions or hydroxyl (H. O.), which is also liberated at the 
surface of the negative metal electrode, is responsible for 
softening scar tissue, some very remarkable results are 
recorded of improvement in scars and cicatrices following 
chlorine ionization, and the author would refer his readers 
to Lewis Jones's work Ionic Medication for further infor- 
mation. 

Perforation of the Root. — When the apex of a root has been 
perforated in the operation of drilling the canal, septic matter 
is likely to be introduced into the periodontal tissue, and in 
spite of ordinary antiseptic precautions inflammation is 
likely to occur. To prevent this, perfect sterilization can be 
ensured by electro-sterilization with 3 per cent, zinc chloride 
or 2 per cent, copper sulphate, passing the iridio-platinum 

1 Ionic Medication, p. 137. 



XECROSIS OF THE JAWS 273 

electrode to the apex or slightly through, and passing 3 ma. 
current for five minutes. The apical foramen being open, 
conduction of current is much greater with a small current 
than in a small unopened foramen with a larger current, so 
that sterilization is effectively carried out with a small current 
strength in a short time. 

Perforation of the side of the canal or at the floor of the 
pulp chamber is an accident which may occur in crooked or 
constricted roots and in large cavities extending toward the 
bifurcation of roots. It is a condition which is regarded by 
many as hopeless. J. F. Colyer says, 1 " When the side of the 
canal has been perforated there is but slight chance of saving 
the tooth." Until the author tried ionic medication in these 
cases he found great difficulty in saving these teeth, especially 
if perforation had occurred some time previously and had 
been the cause of periodontal inflammation, but electro- 
sterilization of the perforation and the whole canal has been 
very successful and proved that perfect sterilization and 
proper subsequent treatment is all that is required to save 
such teeth. Zinc or copper ions with 3 ma. current for five 
minutes imparts a sufficient dose of ions to sterilize the soft 
tissues beyond the artificial opening. A plug of soft gutta- 
percha impregnated with a little iodoform and moistened 
with dentalone on a warm slab, making a thick paste which 
subsequently hardens, should be introduced into the opening 
to fill it, and the canal filled with gutta-percha. The soft 
tissues tolerate this medicated gutta-percha, and usually 
the condition about the root becomes normal and the tooth 
comfortable. Dr. J. W. Spaulding," 2 of Paris, has advocated 
the use of a lead point to close the perforation, and records 
success from the use of this material. 

Necrosis of the Jaws. — Necrosis of the jaws in private 
practice is most often seen in the alveolar process, and is 
generally caused by septic infection following traumatism, 
arsenious acid poisoning, or chronic septic infection of the 
apices of the teeth. In these cases the sequestrum should be 

1 Dental Surgery and Pathology, p. 546. 
- Dental Cosmos. 
18 



274 ELECTRO-THERAPEUTICS IN DENTISTRY 

removed, if separated, or the surface of the necrosed bone 
burred away and the debris syringed out, the affected area 
should then be sterilized with zinc ions at first if there is 
considerable discharge, and followed later with iodine ions. 
A zinc electrode wound with cotton-wool saturated with 2 
per cent, solution of zinc chloride, introduced into the tract 
and 5 ma. current passed from the positive pole for eight to 
ten minutes, according to the extent of the necrosis, will 
impart a sufficient dose of ions to sterilize the part, and 
greatly reduce the sepsis. When discharge is reduced, iodine 
ions are useful in promoting healing; 10 per cent, aqueous 
solution of tincture of iodine conveyed on cotton-wool wound 
about a large platinum electrde with a current of 5 ma. for 
eight to ten minutes according to the severity of the case, 
using the negative pole. 

In chemical poisoning cases from arsenious acid which has 
leaked from a cavity in devitalizing the pulp and caused a 
necrotic area of gums and alveolar border, the affected part 
should be freely cut away with a sharp round burr and 
syringed with warm water ; then a platinum electrode wound 
with cotton-wool and saturated with 10 per cent, tincture of 
iodine and water applied to the part and 2 ma. current passed 
from the negative pole for five minutes. This will often 
arrest the necrosis after a single treatment and terminate a 
painful and threatening condition. 

More extensive necrosis of the alveolus can be treated in 
this manner with zinc and iodine ions to arrest the spread of 
sepsis and shorten the period of healing, and is more effective 
than ordinary irrigation methods. 

A case to illustrate this may be mentioned. A lady was 
sent to me by a throat specialist with necrosis of the alveolus 
extending from the first premolar to the first molar in the 
maxilla on the left side. The first premolar had been 
extracted and a hollow tube inserted into the socket, sup- 
ported in position by a small gold plate. She had worn this 
plate for many months, and was quite expert in syringing 
out the affected tract, which she did many times a day. She 
was certain that she could not do without the drainage tube 



MARGINAL GINGIVITIS 275 

for twenty-four hours as "the pain would be intense," and 
nearly refused treatment when I refused to allow her to 
replace it after the first treatment. The area of exposed bone 
was narrow and about one inch long. Electro-sterilization 
with zinc ions introduced by flooding the area with 2 per cent, 
zinc chloride and a zinc electrode wound with cotton-wool and 
saturated with the solution passed into the opening; 4 ma. 
current from the positive pole for ten minutes was the daily 
treatment for a week. At the end of this time no pus was 
present, and the tract was nearly closed. Iodine ions were 
used for another week, and the lesion healed completely. The 
patient's general health was bad, and the doctor suspected 
toxic poisoning from the sepsis in the mouth aggravating 
existing rheumatoid arthritis. 

The author has not tried the effect of electro-sterilization 
with antiseptic ions in cases of extensive necrosis of the jaws 
resulting from exanthematous fevers, phosphorous, mercury 
or extensive trauma, such as are so frequently caused by 
bullet wounds in this great European war, but bacteria 
infection is always present in these cases and sepsis is the 
greatest difficulty in their treatment ; it seems possible that 
surgical and other treatment would be greatly aided by the 
electro-sterilization of the septic areas. 

Marginal Gingivitis. —A form of gingivitis is sometimes 
met with which is exceedingly painful and difficult to deal 
with; the gingival border is red and inflamed around the 
necks of the teeth, particularly on the external surface for a 
limited distance from the necks of the teeth, but uniformly 
about the entire denture. The dental papilla? between the 
teeth break down and slough on the surface, but there is 
little or no hypertrophy, nor is the inflammation of a pro- 
liferative character. The condition is found in adults, and is 
sometimes associated with digestive disturbances, due to high 
living and free use of wines. The condition resembles the 
acutely painful condition of the gums in ordinary stomatitis 
without the general congestion of the mucus membrane, etc. 
The patient complains of constant pain in the gums, which is 
increased by taking solid food. 



276 ELECTRO-THERAPEUTICS IN DENTISTRY 

In these cases the author has found useful and soothing the 
application of 10 per cent, solution of argyrol on a pellet of 
cotton-wool placed about the necks of three or four teeth at a 
time, a platinum electrode laid flat on this and 0.5 to 3 ma. 
current (according to how the current is tolerated) from the 
positive pole for a few minutes. This repeated about all the 
affected parts relieves the pain and a few such treatments 
usually gives great relief and cures the condition. Other 
local treatment consists in cleansing the teeth and a mouth- 
wash should be prescribed, as well as a light diet and for- 
bidding the use of stimulants. 

Argyrol is a colloid substance (a silver preparation made 
with nucleinic acid) which is not supposed to ionize, but with 
the current it certainly has a soothing and beneficial effect on 
sloughing gums. The author has used it in bad cases of 
stomatitis, which had refused to yield to many other drugs 
applied by painting the gums or mouth washes, and has 
effected complete cures with nothing else but argyrol applied 
with the current. 



CHAPTER XIV. 
TREATMENT OF PYORRHEA ALVEOLARIS. 

Periodontal Disease — Incipient Infection of the Gingival Trough — 
Septic Infection of Gingival Trough without Suppuration — Septic Infec- 
tion of Periodontal Membrane — Acute Septic Infection of Gums and Perio- 
dontal Membrane — Chronic Septic Periodontal Disease. 

Periodontal Disease. — This includes a variety of acute and 
chronic forms of periodontal affections which are not pyorrhea 
alveolaris in the incipient stages, but which invariably lead 
to suppuration of the periodontal membrane, when it is 
correctly termed pyorrhea alveolaris. Definition of terms, 
pathology, etiology, or bacteriology are not the phases of the 
disease with which this work is intended to deal; it is the 
therapeutic aspect which will be chronicled from an electro- 
lytic stand-point. It will be necessary to classify different 
stages of periodontal disease, for which particular kinds of 
treatment are advocated, but before doing so the author 
desires to emphasize the utter futility of trying to cure pyor- 
rhea alveolaris by ionic medication without recognizing and 
removing certain etiological factors, which are always present. 
Electro-sterilization is intended to deal with pathogenic 
microorganisms which are a constant factor; this it does most 
effectively when other factors are taken into account and 
properly dealt with; these may be summed up under the 
heading of local irritants. Irritants in the form of calcareous 
deposits or any form of foreign matter on the surfaces of the 
teeth must be completely removed, and the teeth polished, 
not only above the gum margin but also the roots which are 
denuded of periodontal attachment, rendering the mouth 
in a perfect hygienic state. 

Irritants in the form of ledges, rough or overhanging 



278 TREATMENT OF PYORRHEA ALVEOLARIS 

fillings at the cervical margin, imperfect crowns, ill-fitting 
mechanical appliances, anything that irritates and inflames 
the gingival margins must be removed. 

Irritants in the form of faulty occlusion and undue stress 
must be rectified; these, often most subtle and difficult to 
recognize, are nevertheless of greatest importance and 
demand correction if any form of treatment is to succeed. 

The fulfilment of these conditions in the treatment of the 
disease is often a difficult matter, requiring utmost skill and 
patience, but, if faithfully carried out, the supplementing of 
electro-sterilization of the tissues enhances greatly the lasting 
effect of treatment and shortens the time in which a cure can 
be accomplished. 

There are many who claim good results in the treatment of 
periodontal disease from perfect instrumentation, hygienic 
methods and attention to the existing etiological factors, but 
ignore or else deal lightly with the contingent of existing 
pathogenic microorganisms in the weakened tissues; in the 
hands of these ionic medication would be invaluable in 
promoting a lasting cure of the disease. 

There are many who pass through a long life of practice 
without ever mastering the details of scaling calcareous 
deposits from the roots of teeth. This failure of one of the 
most essential principles in the treatment of periodontal 
disease frustrates every other attempt to cure it. Some are 
convinced that the disease is incurable, and are content with 
vague ideas of " constitutional causes" or " rarefying osteitis," 
as unsurmountable difficulties, and at the same time ignore 
the possibility of local irritation from calcareous deposits as 
an etiological factor of great importance, and rely on the 
forceps as the only real cure for pyorrhea alveolaris. 

For convenience of description the different phases of 
periodontal disease are here classified as follows: 

1. Incipient infection of the gingival "trough" or space. 

2. Septic infection of the gingival trough without suppura- 
tion. 

3. Chronic septic infection of the periodontal membrane 
without visible suppuration — -"dry pyorrhea." 



PERIODONTAL DISEASE 279 

4. Acute septic infection of the gums and periodontal 
membrane without visible suppuration. 

5. Chronic septic periodontal disease with pus. 

1. Treatment of Incipient Infection of the Gingival 
Trough. — Special reference is here made to the gingival 
trough or space because it is the starting-point of general 
chronic alveolar pyorrhea. This space is a normal one, 
formed by the gum margin as it rests on the surface of the 
tooth, the periodontal membrane forming the floor of the 
space (see Fig. 147) . In a very large percentage of healthy 
mouths, if -this space be examined it will be found to contain 




Fig. 147. — A, gingival trough; B, alveolus; C, periodontal membrane. 

some form of foreign matter, rarely, if ever, is it perfectly 
free from deposits of salivary calculus or food debris in a 
state of stagnation and decomposition. 

Incipient infection of the gingival trough may begin at a 
very early age in childhood, dependent entirely on the 
hygienic habits, environment, diet, abnormalities of the nasal 
cavity, etc., but not on the age. Abnormal appearance of the 
gingival margin in children is generally a sign of irritation 
from some cause, but in adults where the mouth is kept in a 
fairly hygienic state, it will be found almost invariably that 
if a flat platinum probe be passed into the gingival trough, 
parallel with the long axis of the teeth, an irregularity of 



280 TREATMENT OF PYORRHEA ALVEOLARIS 

surface or roughness can be detected by the sense of touch 
as the probe passes over the surfaces. 

The gingival trough is always infected by mouth bacteria, 
which are harmless in healthy tissue, but irritation from 
foreign matter causes inflammation which is accompanied by 
infection of pathogenic microorganisms. Just at what stage 
this infection occurs is impossible to demark, but it is prob- 
ably before any outward signs are visible. In order to 
prevent the development of periodontal disease it is advisable 
to cleanse the gingival trough by removing any trace of 
salivary calculus or stagnant food and to polish the tooth 
surfaces. The gums should then be treated by electro- 
sterilization with iodine ions. A platinum electrode should be 
wrapped with a few shreds of cotton-wool, saturated with 
10 per cent, aqueous solution of tincture of iodine. This 
should be passed into the gingival trough and the current 
gradually turned on from the negative pole, the patient 
holding the positive electrode; 2 ma. current should be 
passed while the operator slowly and gradually moves the 
electrode in perfect contact around the necks of the teeth 
wiping out the trough with the cotton and solution. This will 
sterilize the tissue, which may be in the incipient stages of 
infection with pus-producing varieties of microorganisms. 
The gingival margins treated in this manner assume a tough 
and healthy appearance, clinging close to the necks of the 
teeth, and are more able to resist subsequent infection. The 
gingival trough once enlarged by the entrance of foreign 
matter is liable to recurrence of the trouble, and should be 
treated whenever foreign matter is detected. Keeping this 
space clean and healthy is the only means of preventing the 
development of periodontal disease, and is worthy of every 
attention, especially when there is reason to suspect a ten- 
dency to disease. 

Mr. Hopewell-Smith in referring to the " Normal arrange- 
ment of osseous and fibrous tissues" 1 says: u It is the writer's 
belief that not only do all human teeth possess spaces around 

1 Dental Cosmos, liii, p. 981. 



PERIODONTAL DISEASE 281 

their necks, which may become potential cavities for the 
retention of microorganisms, but that if great care be exer- 
cised in the laboratory manipulations, it will be found that 
microorganisms can always be demonstrated in ordinary 
circumstances, occupying the site thus produced. It is when 
they are of the pus-producing varieties that pyorrhea 
alveolaris is established." This being the case, as undoubt- 
edly it is, the method of sterilizing the mucoperiodontal 
tissues referred to must effectively prevent the beginning of 
pyorrhea alveolaris. Sets of teeth which are perfect and gums 
about them which may appear healthy are often in the incip- 
ient stages of periodontal disease, and should be examined 
and treated when foreign matter is present in the gingival 
trough. Endless misery might often be averted by this 
precaution. 

2. Septic Ixfectiox of the Gingival Trough without 
Suppuration. — This is the second stage of local septic perio- 
dontal disease, in which inflammation of the gum tissue is 
discernible; a certain amount of congestion is present, the 
gingival fold is loosened from the neck of affected teeth and 
the trough slightly deepened, making it easy to enter the 
space from which bleeding readily occurs from the inner 
surface. The gingival trough at this stage is found to contain 
food debris and salivary calculus, often extending from the 
enamel surfaces of the teeth which have been badly kept. 
In well-kept teeth nodules of hard, dark calculus, which is 
most tenacious and difficult to remove, may be the only 
irritant in the trough. Inflammation has been caused by the 
presence of foreign substances in contact with the delicate 
epithelial lining of the gingival fold, and the tissues, in this 
state for a considerable time, become the seat of infection by 
pathogenic microorganisms. A process of breaking down of 
the gingival fold, the alveolar bone (see Fig. 148) and surface 
fibers of periodontal membrane is established, which will 
proceed to general chronic periodontal disease if not checked. 
Often the deposit is rough and sharp and chiefly to be found 
in the approximal spaces, causing congestion and the 
bleeding of the interdental papilla?. Treatment consists in 



282 TREATMENT OF PYORRHEA ALVEOLARIS 

thorough instrumentation, removing every particle of foreign 
substance and polishing the necks of the teeth. Ionic medica- 
tion indicated consists in passing zinc ions into the gingival 
trough. A zinc electrode, spear-shaped, of large enough 
size to readily enter the trough should be wound at the 
point with a little cotton-wool, saturated with 3 per cent, 
zinc chloride solution and passed into the space ; the current 
trom the positive pole should then be turned on gradually, 
fhe patient holding the negative electrode. The teeth should 
be kept free from moisture from the mouth, the electrode 




Fig. 148. — Progressing periodontal disease. 

should be very slowly moved around the necks of the teeth, 
which, if not sensitive, will tolerate 2 or 3 ma. current. The 
trough is in this manner sterilized with zinc ions which 
migrate readily even with very much less current strength. 
The time required to go round each tooth should occupy on 
an average about a minute, some places requiring a longer 
time, others less affected, a shorter. Discretion must be 
used in the matter of time required to sterilize soft tissues. 
Ions are conductors of current and move instantaneously, 
the time and current strength work in direct ratio to each 



PERIODONTAL DISEASE 



283 



other to produce depth of penetration. In mucous tissue (2 
ma. current with a small area electrode) the current density 
is very great, and the dose of ions provided in one minute 
over a small area of a gingival border must be considerable. 
One treatment will ofteri be sufficient if all foreign matter 
has been completely removed, and the teeth polished, but 
the patient should be seen in three or four days, and if this 
condition has not been fulfilled, redness and congestion will 
be present wherever any irritant is lurking. This should be 
removed, and the affected part treated as before. The gums 
by this treatment will resume a normal appearance, and con- 
tract about the necks of the teeth, restoring nature's barrier 
to the introduction of food debris into the gingival trough, 
and averting subsequent periodontal disease. 





Fig. 149 



Fig. 150 



3. Chronic Septic Infection of the Periodontal 
Membrane without Visible Suppuration — "Dry Pyor- 
rhea." — This phase of periodontal disease is most subtle and 
is rarely recognized in the incipient stages. The irritation set 
up in the gums by the presence of foreign matter and bacteria 
infection is confined to the inner surface of the gingival fold, 
extending to the dental ligament, which it destroys by a slow 
process, the conical border of alveolar bone is affected, and grad- 
ually absorbs by a process of rarefying osteitis (see Figs. 149 
and 150), the superficial fibers of periodontal membrane are 



284 TREATMENT OF PYORRHEA ALVEOLARIS 

destroyed to a considerable depth before the necks of the 
teeth become exposed. The gums are thinned and become a 
mere layer of tissue, which clings closely to the necks of the 
teeth; the interdental papillse disappear, and spaces appear 
between the teeth over the alveolar bone, which has absorbed 
at the margins; the teeth are usually quite firm. It occurs 
in well-kept mouths and is often attributed by dentists to 
overbrushing or associated with gouty or rheumatic diathesis, 
being termed by some authors " gouty periodontitis which is 
rarely recognized before the age of thirty." The author 
considers this " gouty diathesis" a coincidence, which has 
little to do with the direct cause and progress of the disease, 
except for the augmenting of an irritant in the form of minute 
granular deposits of hard calculus, which adhere firmly to the 
roots of the teeth, and in the first instance starts the inflam- 
matory action of a subtle and slowly progressive character. 
A flat probe passed into the gingival trough between the thin, 
taut layer of tissue and the roots of teeth will reveal consider- 
able loss of periodontal attachment, and always a layer of 
calcareous deposit, sometimes of dark, hard nodules, but 
more often of a finely granular nature, most difficult to detect. 
This form of the disease is difficult to deal with. If recognized 
in the early stages the gums are not wasted, and the removal 
of the calculus is not as difficult as later when a thin stretched 
layer of tissue resists the proper use of scalers and the polish- 
ing process. Treatment consists in removal of every particle 
of irritant, and sterilization of the infected gums and perio- 
dontal tissue. Electro-sterilization is often painful, owing to 
the sensitive nature of the roots of the teeth and the thinness 
of the gums. A thin platinum or zinc electrode should be 
wrapped with a few shreds of cotton-wool, saturated with 3 
per cent, zinc chloride and passed into the gingival trough, the 
current from the positive pole should be slowly turned on, the 
patient holding the negative electrode. If the teeth are sensitive 
0.5 ma. current may be all that will be tolerated in the incisor 
region, but the molar region will usually admit of 2 or 3 ma. 
The electrode should be slowly moved parallel with the long 
axis of the teeth around the necks, with the object of steriliz- 



PERIODONTAL DISEASE 285 

ing the gingival trough. The tissue overlying the roots of 
the teeth is very thin, and the time required to sterilize the 
neck of a tooth must be in ratio to the current strength, 
varying from half a minute to one minute. 

The number of treatments required depends upon the 
severity of the case, and the current strength available. 
Three the first week, two the second, and once a week after 
until every sign of inflammation about the gingivus has 
disappeared, gives some idea of the course that should be 
pursued in combating this affection of the gums. Fetid 
odor is often complained of by patients and is sometimes the 
only discomfort. Until this disappears entirely the treat- 
ment should be vigorously continued every second day, after 
which the intervals should be extended to every third day, 
and later to once a week. Fetor is usually due to disease in 
the molar region, and here a larger current strength is gener- 
ally tolerated and should be used, in order to carry out 
sterilization. The daily use of an antiseptic lotion on the 
brush should be insisted on. The restoration of lost bone 
and gum tissue cannot be looked for in these cases; the 
arresting of the progress of the disease is all that can be 
accomplished, and this can only be effected by stopping 
infection of pathogenic microorganisms, which have taken 
hold of the weakened tissues. One case of many the author 
has successfully treated may be mentioned in support of the 
value of zinc medication in this phase of the disease. Lady R. 
consulted me eight years ago for "receding gums," The 
necks of the maxillary incisors and cuspids were exposed 
and the premolars and molars showed signs of the trouble; 
the teeth were highly sensitive to thermal changes and also 
to electric current. Subgingival calculus of a hard, dark, 
granular type was found beneath the gum margin on every 
tooth, and principally in the interspaces, the dental papillse 
had disappeared from the interspaces of the superior incisors. 
The teeth were free from caries and beautifully white, even, 
and well kept. She informed me that her dentist had cleaned 
her teeth four times a year, still the receding gums was pro- 
gressing. The gingival trough was treated (after deposits 



286 TREATMENT OF PYORRHEA ALVEOLARIS 

had been removed) with zinc and iodine ions. At the first 
course of treatment, which extended over six weeks at 
intervals of three and four days, the current strength of 
0.5 to 1 ma. was all that could be used on the anterior teeth on 
account of sensitiveness of the necks of the teeth. One 
treatment with zinc ions was given at intervals of four months 
for a year after the first course, and the gingival trough 
examined for deposits. Since then the patient has been seen 
twice a year, and when any irritant was discovered in the 
gingival trough it was sterilized as before. The sensitiveness 
has gradually disappeared, and at a recent sitting it was 
possible to pass 4 ma. current about the interspaces of the 
superior incisors, where previously it was painful to 0.5 ma. 
Zinc ions act slowly but surely as an obtundant to sensitive 
dentine. In this case the " dry pyorrhea" has been completely 
checked, and the author does not think that cleaning alone 
would have been effective; the electro-sterilization of the 
gingival trough is a necessary adjunct to effect a permanent 
cure of this slowly progressing septic destruction of the 
periodontal tissue and alveolar bone. 

4. Acute Septic Infection of the Gums and Perio- 
dontal Membrane without Visible Pus. — This stage of 
the disease is marked by congestion of the gums, the papillae 
are enlarged and heaped up between the teeth in loose tags, 
which bleed freely when touched; the gingival trough is 
much deepened by the loss of dental ligament, inflammation 
of the gingivus is general. This stage is a continuation of the 
second stage described in this series, and is marked by greater 
stagnation areas and greater accumulations of foreign sub- 
stances, debris of soft food in stages of decomposition and 
quantities of calcareous deposits extending into the gingival 
trough. In young subjects this condition is often associated 
with lack of proper masticating function, mouth-breathing 
and imperfect brushing. In adults the only cause is irritants 
in the gingival trough — tartar and food debris. The gums 
become tender, bleed freely and proper brushing is impossible. 
This may be the condition extending to the entire denture 
without any deep pockets yet formed, or may be the con- 



PERIODONTAL DISEASE 287 

dition of a certain area, other parts being less affected, or may 
be the area leading up to a much worse area of infection, 
which has succumbed to the ravages of chronic pyorrhea 
alveolaris. The clinical appearance varies considerably, 
but is marked by considerable inflammation without risible 
pus. 

Treatment consists in removing the irritant cause; this 
excites free bleeding and is painful, making it impracticable 
to carry out electro-sterilization at first, but the inflamma- 
tion subsides quickly after the gingival trough is cleansed 
and ionic medication with zinc or silver ions soon arrests 
the inflammatory progress. Electro-sterilization should be 
carried out with 3 per cent, zinc chloride, or 2 per cent, silver 
nitrate in cases where there is sloughing of the borders of the 
interdental papillte. A platinum or zinc electrode, wound with 
a few shreds of cotton-wool and saturated with the solution, 
should be used to slowly wipe out the gingival trough with 2 
or 3 ma. current, keeping the electrode in good contact with 
the tissues while moving it, and frequently turning off the 
current to replace fresh wool and more solution when bleed- 
ing of the tissues interferes. Two or three treatments with 
zinc ions at intervals of three days will often be sufficient to 
reduce the inflammation, and produce a healthy reaction of 
the gums. 

Polishing the surface of the teeth after removal of salivary 
calculus is necessary, and as soon as brushing with a stiff 
brush is possible the patient should be instructed hi a useful 
daily hygiene with antiseptic lotion on the brush. The 
ionic medication should be continued until every sign of 
inflammation subsides, which will not occur if any trace of 
irritant is left in the gingival trough or on the surfaces of the 
teeth in contact with the gum margins. Patients should be 
warned that this attack of gingivitis is the forerunner of 
pyorrhea alveolaris, and with deepened gingival trough and 
weakened alveolar border recurrence is very liable to occur 
if strict attention is not paid to daily hygiene and gum 
massage with a stiff brush. 

The eradication of pathogenic organisms in the tissues is 



288 TREATMENT OF PYORRHEA ALVEOLARIS 

accomplished by the electro-sterilization and so long as 
irritation and inflammation of the tissues are prevented the 
mouth organisms can have no influence on the tissues. 

5. Chronic Septic Periodontal Disease with Pus. — 
This stage of the disease is simply a continuation of those 
already described, there is never a starting-point of pyorrhea 
alveolaris below a healthy gingival border, and it is a matter 
of impossibility for pus-yielding pockets about teeth to be 
established without the incipient stages of periodontal disease 
being passed. Special attention has been drawn to the early 
stages of periodontal disease with the express purpose of 
saddling the responsibility of occurrence of pyorrhea on those 
who neglect the proper care of the gingival trough for their 
patients. Endless misery could have been saved to a host 
of people now suffering from pyorrhea if their dentist had 
but recognized and treated the incipient stages of periodontal 
disease and warned those people of the importance of proper 
hygienic preventive methods. Many people, of course, have 
themselves only to blame from neglect or ignorance. From 
whatever cause, unfortunately, we are often called upon to 
treat the disease in the stage when it has progressed con- 
siderably; the periodontal membrane has been destroyed 
to a considerable depth, pus-yielding pockets are established 
and rarefying osteitis is in progress, with septic infection of 
the hard and soft tissues. The general symptoms and 
clinical appearance of the disease are well known and descrip- 
tion is unnecessary here. 

Treatment by ionic medication is intended to deal with one 
etiological factor, which, at this advanced stage, is a great 
menace to the surgical side of the work. Pathogenic micro- 
organisms lurk in the tissues, enter the alveolar bone and are 
readily absorbed into the general circulation. It is to destroy 
deep-seated bacteria, that electrolytic sterilization is specially 
adaptable. 

Clinical proof of the antiseptic nature of electrolytic ions 
of zinc, copper, silver, etc., has been recorded by the highest 
authorities (see p. 244) and the author has experimentally 
demonstrated that the depth of penetration of dissociated ions 



PERIODONTAL DISEASE 



289 



in the soft tissues and alveolar bone is very considerable with 
a small current strength in a very short time (see p. 209). 
On these two requirements hinge the great usefulness of this 
method of treating pyorrhea. In treating advanced cases 
there are always many etiological factors to be taken into 
account, in order that success may be assured in overcoming 
the one for which electro-sterilization is required. 

Radiographs of roots of the teeth should first be obtained. 
This is best done in sections of four teeth at a time, the film 
inside the mouth. Condition of the bone, depth of pockets, 
calcareous deposits, faulty fillings and crowns are thus 
exposed. The radiographs should be referred to at intervals 
while treating the various parts of the mouth. Figs. 151 





Fig. 151 



Fig. 152 



and 152 show upper and lower teeth of a case treated in June, 
1913. The patient had received peremptory orders from her 
medical adviser to have every tooth extracted. This advice 
had been given on account of the toxemic effect of pus from 
the mouth, causing malaise and rheumatism in the shoulder- 
and knee-joints, by which the patient was nearly crippled. 
Her dentist had agreed that extraction was the only course to 
follow. 

Treatment consisted in removing quantities of hard sub- 
gingival tartar, thorough instrumentation and perfect polish- 
ing of the necks and roots of teeth. This was accomplished 
only by repeatedly searching under the gums for particles, 
which, owing to the hard, tenacious nature of the deposit, 
19 



290 TREATMENT OF PYORRHEA ALVEOLARIS 

were difficult to eradicate completely. At each treatment, 
after scaling and polishing for half an hour, ionization was 
carried out for half an hour, the patient having the negative 
electrode, a zinc positive electrode was wound with a few 
shreds of cotton-wool and saturated with a solution of 3 per 
cent, zinc chloride. This was passed to the bottom of the 
pockets between the teeth and 3 to 5 ma. current passed for 
half a minute to two minutes. The gingival trough was 
ionized by slowly moving the electrode out of the deeper 
pockets around the necks of the teeth, every part of the 
tissues comprising the trough was treated. Treatment was 
carried out every second day, most attention being given to 
pockets which were deepest, and from which pus could be 
expressed. Four crowns and a faulty filling shown in Fig. 152 




Fig. 153 

and 153 were removed, these being the chief cause of sepsis 
in the molar region. In every instance after the removal of 
the irritant cause and ionization, pus ceased and condition 
improved. Treatment was kept up until the gingival trough 
was perfectly healthy ; and bleeding, which at first was exces- 
sive, completely ceased even when instruments were forcibly 
passed under the contracted gingival border. 

The case, which was undertaken on June 10, 1913, required 
eight treatments that month, during which time malaise 
completely disappeared and rheumatism greatly improved. 
Five treatments were given up to July 24, on which date 
every symptom of pyorrhea had disappeared and also the 
rheumatism. The patient was instructed in a useful method 
of daily hygiene and a benzoic acid wash prescribed as follows : 



PERIODONTAL DISEASE 291 

T$ — Thymol gr. iij 

Benzoic acid 3ss 

01. cinnam . ITlx 

Acid carbolic ITlxxx 

Otto Rosse Tflxv 

Alcohol ad giv— M 

Sig. — A few drops on the wet brush twice a day. 

The management of cases after treatment is of vital impor- 
tance. This one was seen once a month for three months, 
and wherever the slightest redness of the gingival border was 
detected treatment was repeated, and the patient's attention 
was drawn to the cause, which was invariably neglect to com- 
pletely remove lodgments of food. During the next year the 
teeth were thoroughly polished every four months and since 
every six months. There has been no recurrence of pyorrhea 
or rheumatism for four years. Should any particular part 
become affected in future one or two treatments will be all 
that is necessary to restore the parts. The case is typical of 
what can be done by electro-sterilization of pyorrhea to bring 
about what can be rightly claimed to be a complete cure of 
the disease. 

A viscid, glairy mucus is often present which coats the 
teeth and adheres closely to the surfaces. This should be 
systematically removed at each treatment by brushes on the 
engine with powdered pumice made into a paste with an anti- 
septic mouth wash and ipecacuanha tincture, equal parts, 
leaving all the teeth highly polished after each sitting. This 
mucus coating will generally disappear when the disease is 
cured, but occasionally the mucous glands about the mouth 
become infected with pyogenic microorganisms, and exude a 
sticky mucus approaching the appearance of pus, which the 
patient may mistake for pus from the gingivus. Should this 
occur, the surface of the gums and mucous membrane on the 
buccal and labial aspect should be treated by placing a layer 
of cotton -wool saturated with 2 per cent, zinc chloride on 
the gums, pressing it into place with a flat zinc electrode, 
and passing 5 to 10 ma. current for two to four minutes 
on a surface of about an inch long, repeating this all around 
the mouth until the entire gum surface has been ionized. Two 



292 



TREATMENT OF PYORRHEA ALVEOLARIS 



or three such treatments will sterilize the tissues and change 
the secretion to normal consistency. 

Faulty occlusion and undue stress on one or more teeth 
will keep up an irritation to the periodontal tissue and bone, 
which will defy all treatment. This condition must be 
corrected, or no amount of ionization will avail. It is desir- 
able to ligature loose teeth together, holding them firmly in 
the sockets until all inflammation is reduced and the hard 
and soft tissues being thoroughly sterilized, a fresh deposit 
of alveolar bone is formed about the roots and the teeth 
become firm. All necessary instrumentation and polishing 
should be done before ligaturing, and ligature wire should be 
so placed that it cannot slip down on the gums, and the patient 




Fig. 154 



must be instructed how to keep the interspaces clean. In 
cases of great loss of bony attachment permanent splints fixed 
to the lingual surface of the incisor teeth are useful in retain- 
ing the teeth and rendering them functional for a number of 
years. Teeth which have taken up abnormal positions — 
been displaced by the disease affecting one surface only, like 
the approximal surface of incisors — should, after instrumenta- 
tion, be treated by electro-sterilization and replaced in 
normal position and retained there. Splints are in those 
cases a great advantage. Fig. 154 shows a case of the kind 
treated over ten years ago, which has been cured by this 
means and the spread of the disease completely checked. 
The clinical aspect of the gingival border and alveolus 



PERIODONTAL DISEASE 293 

after treatment and general prognosis must now be referred 
to. After thorough instrumentation, polishing of the teeth 
and treatment with electro-sterilization, invariably improve- 
ment in the general aspect of the gums is noticeable, but 
experience shows that this does not constitute a cure, often a 
refractory pocket here and there may continue to exude pus, 
or pus may be expressed if great care is taken to find it. 
This is nearly always a sign that a special cause is at work, 
either a particle of calculus left beneath the gums, undue 
stress, or some irritant cause, which must be removed and 
ionization vigorously continued with an increase of the time 
and current strength to that particular part. Even after all 
signs of discharge have disappeared, the contraction of the 
gum tissue on the necks of teeth must be noted, and no hope 
of permanent results can be expected if the gingival trough 
remains wide open to receive food debris at every meal. 
Ionization must be continued until it is fair to expect that the 
reasonable cooperation of the patient is sufficient to prevent 
stagnation in the gingival trough. This is always possible 
if in the first instance proper judgment has been exercised in 
the removal of such teeth as are so hopelessly involved that 
treatment will be useless. This does not mean that all 
loose teeth or teeth with deep pocket should be extracted, 
these can often be restored to perfect health. The regenera- 
tion of bone about the sockets of pyorrhea teeth is an 
established fact, although seriously doubted by some eminent 
authorities. Mr. Hopewell-Smith 1 in his concluding notes on 
"Pathohistology" of pyorrhea alveolaris, referring to the 
treatment of the disease says: "The hopelessness of retaining 
the teeth and of building up bone which has been lost by 
absorption or the recalcification of decalcified foundations 
must be apparent. The treatment, at best, can only be 
palliative, and, unfortunately, only directed to a preven- 
tion of further destruction, and not the rehabilitation or 
reconstruction of parts absolutely forever destroyed." The 
writer is convinced that alveolar bone seriously affected by 

1 Dental Cosmos, liii, 991. 



294 TREATMENT OF PYORRHEA ALVEOLARIS 

chronic pyorrhea is capable of reformation about the sockets 
of loosened teeth. Instances are constantly seen where 
teeth are exceedingly loose, moving freely in enlarged sockets 
(as is always the case in faulty occlusion or undue stress), 
but when, under treatment, all irritant causes are removed 
and the septic infection dealt with, the rarefied bone recalci- 
fies and the sockets reform about the roots, leaving them 
in a firm, healthy condition. Proof is also furnished by radio- 
graphs taken before and after treatment (Figs. 158 and 159). 
It is not useless or hopeless to retain a set of teeth, which is 
badly affected by pyorrhea, in a functional state for a space 
of fourteen years or even six years, provided the septic 
infection can be kept away, even if it is necessary to treat the 
teeth two or three times a year in order to obtain such 
results. 




Fig. 155. — Case C, model 1 before treatment, and 2 fourteen years later. 

The Case C, reported on p. 240, is one in which exten- 
sive pyorrhea witn constitutional symptoms accompanying 
it existed, the pockets on the palatal aspect of the incisors 



PERIODOXTAL DISEASE 



295 



extended nearly to the apices, every symptom of chronic 
pyorrhea existed. When the teeth were retracted to the posi- 
tion of the diagram on p. 2-L1 they were so loose that they 
could be moved forward a distance of about 5 mm. without 




Fig. 156. — Radiograph January 29, 1907. 

touching a bony socket. The bone has reformed in those 
empty sockets, and not only reformed but grown thicker on 
the labial aspect of the alveolus than is normal, as shown 
by the photograph of the models taken before treatment 
and fourteen years later [(Fig. 155). The recurrence of 




Fig. 157.— Radiograph May 30, 1912. 



pyorrhea has not taken place, no teeth have been lost and 
the once diseased dentine has been functional for over four- 
teen years. 
On January 29, 1907, the accompanying radiograph was 



296 TREATMENT OF PYORRHEA ALVEOLARIS 

taken of a patient suffering from every symptom of pyor- 
rhea including constitutional disorders. This radiograph 
was sent to Mr. C. Clark, of London, with the patient on 
May 30, 1912, with a request to produce a picture of the 
same parts. The result will be seen in the radiograph, Fig. 
157. It will be seen that the alveolus has changed consider- 
ably in five and one-half years; between the second premolar 
and the cuspid carrying a bridge the bone has quite a differ- 
ent contour, it is a higher level, there is more alveolar process 
about the molar roots, and the posterior boundary of the last 
molar has a growth of alveolus resembling a molar, which is 




Fig. 158. — Radiograph December 7, 1906. 

new bone. Allowing for a slight difference of angles at 
which the radiographs were taken, there is still a marked 
difference in the appearance of the bone, the first shows 
marked decalcification and morbid changes, the second shows 
a reformation of bone about the roots of the teeth. The 
clinical changes are no less marked, the pyorrhea has entirely 
disappeared, the gums are healthy and the teeth firm. The 
pyorrhea was treated with zinc ions. 

Another example is shown in Fig. 158; radiograph taken on 
December 7, 1906, which shows pyorrhea started about the 
superior incisors; this case was treated with zinc ions. The 



PERIODOXTAL DISEASE 



297 



radiograph taken on June 6, 1912, shows that no change 
has taken place in the bone surrounding the roots of the 
teeth, except possibly a denser calcification. This appear- 




Fig. 159.— Radiograph June 6, 1912. 



ance, however, may be clue to the difference in length of 
time in exposure when taking the radiograph, but the loss of 
bone was no more than it was six years previously. The 
progress of the pyorrhea has been checked by a few treat- 




Fig. 160.— Radiograph January 29, 1907. 

ments of zinc ionization and subsequent half-yearly treatments 
which consisted chiefly in thoroughly cleaning the teeth. 

The next radiograph taken January 29, 1907, shows a bad 
case which has been cured, and the discharge has not returned 



298 



TREATMENT OF PYORRHEA ALVEOLARIS 



since treatment five and one-half years ago, although it has 
required constant attention to keep it from relapse, owing 
to the faulty articulation and constant irritation thereby. 
It will be seen that the teeth in the second radiograph (taken 
May 30, 1912) have been ground on the occluding surfaces 
to correct this. The teeth are functional and not very loose, as 
would be expected by the appearance of these radiographs. 




Fig. 161.— Radiograph May 30, 1912. 



It makes the greatest difference to people affected with 
pyorrhea to this extent if by treatment they are able to 
retain their teeth for years, and are saved the wearing of 
plates, which usually act as irritants and lead to the loss 
of the entire denture from progressive periodontal disease. 

A healthy fibrous tissue forms about the teeth in these 
cases which holds them firmly in position, and if kept from 
bacterial infection (as they can be by ionic medication) 
they are retained and are functional. 

It must not be thought that the disease is curable at 
any stage by simply ionizing the periodontal tissue and 
alveolus. There are many conditions which arise that 
defy all treatment. It is difficult to formulate any rule 
to classify the teeth which should not be treated by any 
other means than by extraction. 

In determining the necessity for extraction of teeth, judg- 
ment should be exercised at the outset, and circumstances 
attending each individual case should be carefully weighed. 



PERIODONTAL DISEASE 299 

If constitutional disorders of any kind accompany the local 
symptoms, and if medical opinion points to the supply of 
small doses of toxins being the cause of the constitutional 
disturbances, it would be unwise to attempt to retain such 
teeth as cannot be kept in a perfectly aseptic condition by 
the patient after treatment, such as multirooted teeth 
with pockets that extend under the bifurcations, or teeth 
with pockets extending to the apices destroying the pulp, 
or teeth which with the adjoining one form V-shaped spaces, 
wholly inaccessible by the patient; whenever proper daily 
hygienic methods are impossible for the patient, individual 
teeth which are the cause of keeping up a septic foci 
should be removed at the commencement of the treatment. 

The author has never seen a case in which it was necessary 
to extract a whole set of teeth to relieve constitutional dis- 
turbances from toxemia. If the toxins from pyorrhea are the 
potential source of the trouble, it is invariably the case that 
the periodontal disease is not so general as to make it impos- 
sible to cure the least affected teeth, and the removal of those 
which cannot be made aseptic and kept so will relieve the 
constitutional disturbances, at the same time retaining organs 
of mastication, which are just as vital for the health of the 
patient as the radical removal of the source of toxins. 

Teeth which have to be extracted or been lost previously 
to the case coming under treatment should be replaced by some 
mechanical means which will ensure the restoration of balance 
of the entire denture, and relieve undue stress on any par- 
ticular location, special care being exercised not to furnish 
an irritant to the parts on which this artificial restoration is 
dependent for its attachments. 



CHAPTER XV. 

ELECTRICITY FOR ANESTHESIA, FOR BLEACH- 
ING, AND FOR NEURALGIA. 

Anesthesia- of Sensitive Dentine — For Immediate Extirpation — Anes- 
thesia of Gums and Alveolus — Electric Tooth Bleaching — Bleaching with 
Chlorinated Lime — Bleaching with Hydrogen Dioxide — Neuralgia. 

ANESTHETIC APPLIED BY ELECTRIC CURRENT. 

Anesthesia of Sensitive Dentine. — The anesthetic effect of 
cocaine on sensitive dentine when applied by the electric 
current is well known. In America the interest of the 
dental profession was attracted to this subject by W. J. 
Morton in 1896, who attributed the effects to cataphoresis. 
A mass of literature has since appeared from time to time 
setting forth the advantages and disadvantages of anesthesia 
of dentine by electrical application of cocaine. 

The use of the current for this purpose has often been 
brought into disrepute by the lack of knowledge of general 
electro-therapeutics. Cataphoresis has been the only effect 
thought of, and it has not been realized that cocaine ions 
penetrate dentine with a very low current strength, and that 
if the electrical application of the drug is pressed too far 
complete anesthesia of the pulp takes place, when it may 
be only desired to benumb the sensitive surface of the den- 
tine. 

As has been pointed out already in this work the effect 
of the electric current on cocaine is not an electro-osmotic 
effect in the sense of propelling the solution of cocaine 
en masse into the dentinal tubuli by cataphoresis, but it 
is ionic in the sense that the particles of cocaine are dis- 
sociated in the solution containing them, and being elec- 
trically charged are conveyed by conduction into the organic 



ANESTHETIC APPLIED BY ELECTRIC CURRENT 301 

structure of the dentine on which it has an anesthetic effect. 
The depth of penetration of cocaine ions will depend on the 
organic structure of the tooth and the current strength which 
is used. 

Cocaine ions penetrate the superficial layer of sensitive 
dentine with a current strength of only 0.5 ma. and produce 
anesthesia. With a stronger current the effect is more 
rapid and the penetration is deeper. Failure to produce 
the anesthetic effect in a few minutes is usually due to 
faulty technic. If the electrode is placed on a surface of 
dentine so that the current is only passed from a small 
area (see Fig. 162), the area in contact with the metallic 




Fig. 162. — Imperfect technic. 

conductor only will be affected by the passing of cocaine 
ions, and penetration will be greatest at the point of contact. 
In order to obtain perfect anesthesia of the whole surface 
which it is desired to affect, the electrode should cover 
the whole area. This ensures the passing of ions into 
all the organic matter exposed to conduction of current, and 
the larger the area the less painful will the process be, as 
the density will be lessened by the increase of area of the 
electrode. 

To anesthetize dentine in the cavity of a tooth, a 5 to 
10 per cent, aqueous solution of codraline, novocain, cocaine, 
or any of the cocaine preparations now in use, should be 



302 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 

placed into the cavity on a pellet of cotton-wool and should 
be warmed to 99° F. On this should be fitted a piece of plati- 
num foil sufficiently large to cover the whole area of the cavity 
and to this a platinum anode applied. The current should 
be turned on gradually until it is felt by the patient, when it 
should be allowed to pass for a minute, and increased until 
again felt. Except it is desired to anesthetize the pulp, 
current should never be raised to the strength of 4 ma., for 
should it be possible to pass this amount of current without 
pain the pulp will then be found to be anesthetized and can 
be removed without pain. 

A point in technic which has already been insisted upon, 
but which may not have been especially noticed, is here 
again referred to, i. e., when a voltaic cell battery is used it 
should never be of that kind which is provided with a 
"current collector" alone, if it has a current collector (that is, 
a switch with studs representing each cell of the battery) it 
should also have a finely graded rheostat of graphite or 
German silver wire with sliding contact, which permits of 
only a fraction of a volt increase of E. M. F. when the resist- 
ance is decreased by moving the shunt of the rheostat; the 
current strength will then be increased by a fraction of a 
milliampere, and no shock is possible with this gradual 
increase of current. If stud contact points are used alone, at 
contact with each stud the E. M. F. is increased by 1 volt in 
some batteries and by 1.5 volts in others, according to the 
voltage of the cells composing them. This means that the 
current strength is also abruptly increased as will be indi- 
cated by the milliamperemeter, according to the resistance 
in circuit. In soft tissues like periodontal tissue increase of 
1 volt will sometimes increase the current strength consider- 
ably. In dentine, owing to the great resistance of that tissue, 
the increase might be only 0.1 ma., but the shock of sudden 
increase of E. M. F. is even more severe than in soft tissues. 

It is undesirable to anesthetize a pulp except it is to be 
extirpated, for in some cases it dies subsequently, apparently 
from the effects. 

The influence of the current upon pulps which have been 



ANESTHETIC APPLIED BY ELECTRIC CURRENT 303 

anesthetized is a debatable point. It has been pointed out by 
some authorities that the death of the pulp may ensue, by 
others that no ill effects take place. Dr. Louis Jack 1 states 
"in deep cavities nearing the pulp, the effect extends to 
that organ. The recurrence of sensitivity takes place within 
a few hours. Xo injury appears to follow." This may not 
always be the case. In some cases if anesthesia is pressed to 
the point that the pulp is anesthetized the subsequent death 
of the pulp takes place. There is a scientific electrical reason 
for expecting this result, which has been demonstrated by 
experiment and in practice. If a platinum electrode is placed 
in albumin and a current of 2 or 3 ma. passed, coagulation 
takes place about the electrode. The electro-positive effect 
on blood is also to coagulate it; this effect is obtained in the 
treatment of aneurysm by electrolysis. If the albuminous 
ingredient of the pulp be coagulated by the passing of the 
current, which would undoubtedly be the case if 4 or 5 ma. 
of current is passed, the effect would be stasis and death 
of the pulp in the majority of cases. The cocaine would 
be absorbed and taken into the general circulation, and is 
not an element of danger in this respect. 

The opinion that coagulation of albumin is the effect 
accountable for the death of the pulp, when it occurs after 
cocaine anesthesia is simply one of conjecture yet to be 
proA^ed. 

Dr. Finzi 2 points out that when cocaine is driven into 
the skin with an electrode 3x3 cm. with a current strength 
of 10 to 15 ma. for ten minutes, anesthesia of the area 
treated, of a very transitory nature, is produced but is fol- 
lowed by hyperesthesia and hyperemia, which persists for 
days. If this effect is also produced on the pulp tissue 
it would be sufficient to cause death of the pulp. The 
epidermis being of very different vascular construction from 
pulp tissue, hyperesthesia and hyperemia may possibly be 
averted by vascular absorption, and death of the pulp 
avoided in many cases; still there is the liability, from one 

1 Text-book on Operative Dentistry (Kirk), p. 167. 

2 British Medical Journal, November 2, 1912. 



304 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 

cause or another, of death of the pulp to follow cocaine 
anesthesia by electrotherapy. 

For Immediate Extirpation. — For immediate extirpation 
of the pulp of a sound tooth a small opening should be 
made through the enamel opposite the nearest point to 
the pulp. When sensitive dentine is reached the drill hole 
should be lined with a pellet of cotton-wool saturated with the 
anesthetic and to this applied a platinum electrode of about 
the diameter of the hole; 0.5 to 1 ma. current should 
then be passed from the positive pole for a few minutes, 
at the termination of that time it will be possible to drill 
deeper toward the pulp, and if still sensitive a similar appli- 
cation should be made, slowly increasing the current strength 
to 3 or 4 ma. This will ensure the possibility of opening the 
pulp chamber; then a further application for a minute will 
produce complete anesthesia of the pulp. The electrode in 
this operation should be pressed firmly into position and kept 
steadily there, so as not to vary the resistance which in 
dentine is considerable owing to the small amount of organic 
matter. The current should be turned off before removing 
the electrode. 

The ordinary precaution of isolating the tooth and keeping 
away saliva by application of rubber dam is advisable, 
although it is not always necessary to apply the rubber dam. 
Excess of cocaine may produce toxic effects by leaking 
into the soft tissue about the necks of the teeth, or by the 
passing of ions into the circulation through the pulp itself. 
It is therefore advisable to use cocaine mixed with adrenalin 
chloride, or novocain. 

The operation of stapling or splinting incisors in pyorrhea 
cases is greatly facilitated by this method of anesthetizing 
the dentine and pulp. It is often advisable to remove the pulp 
from pyorrhea teeth which are to be stapled. This can be 
readily done by exposing the dentine in proximity to the 
pulp in the position of the receptacle for the pins necessary 
to form the staple. Then the teeth can be anesthetized with 
codreline, using a current of 3 or 4 ma. 

In cases of inflammation of an exposed pulp when pres- 



ELECTROLYTIC TOOTH BLEACHING 305 

sure anesthesia is often impossible, cocaine ions can be 
used to produce complete anesthesia. The conduction of 
current is the same in inflamed tissue as in healthy tissue, 
and ions migrate just as effectively in one as the other. When 
the pulp is exposed, a minimum of 0.2 ma. current may be 
all that can be tolerated, but ions are conducted even at this 
low current strength, and it will be found that after a 
minute or two of passing this current it is possible to increase 
the strength gradually until anesthesia ensues, when 3 or 4 
ma. can be passed without discomfort. 

Anesthesia of the Gums and Alveolus. — Anesthesia of 
the gums and alveolus for extraction can be successfully 
carried out by Dr. W. J. Morton's 1 method of applying 
a metallic-lined rubber cup electrode to both sides of the 
gums about the teeth, but this method is more difficult and 
less sure for this purpose than hypodermic injections as now 
generally practised. 

ELECTROLYTIC TOOTH BLEACHING. 

Discoloration of teeth due to chemical changes of the 
organic contents of the dentinal tubuli and also absorption 
by the tubuli of putrescent products of the dead pulp 
tissue provides one of the knotty problems which often 
taxes the skill of the careful and ingenious operator to the 
utmost. The subject of the chemistry of tooth discolora- 
tion has been ably expounded by Dr. E. C. Kirk, 2 who states 
that a the proteid elements of the pulp tissue are complex 
combinations of carbon, oxygen, hydrogen, nitrogen, sulphur, 
and phosphorus, which in the gradual breaking down of the 
process of putrefactive decomposition are split up finally 
into dioxide, water, ammonia, and hydrogen sulphide, with 
possibly the formation of traces of phosphatic salts." The 
principle of bleaching teeth should aim at the transfer of 
this chemical combination which causes the discoloration 
into a new combination by the addition of a fresh molecule, 

1 Cataphoresis, p. 222. 

2 Text-book of Operative Dentistry, p. 524. 
20 



306 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 



which has the property of combining to form a compound 
of transparent or translucent appearance. This fresh 
molecule has long been known to be oxygen in its nascent 
state, the difficulty has been to procure it and to transmit it 
to the dentine tubuli containing discolored organic matter. 

The most effective bleaching agents are calcium hypo- 
chloride or chlorinated lime, chlorinated soda, hydrogen 
dioxide, sodium dioxide, and pyrozone (an ethereal solution 
of H 2 2 ). All these can be applied to the dentine of dis- 
colored teeth for their bleaching qualities more effectively 
with an electric current than without. 





Fig. 163 



Fig. 164 



Bleaching with Chlorinated Lime. — The general principles 
of technic in bleaching have been referred to under that 
heading in another part of this work and must be observed 
in the bleaching operation. The tooth must be prepared 
so that the two electrodes can be placed in it a little distance 
apart, but not separated by a portion of tooth structure; 
there should be liquid contact completing the circuit between 
the two poles. Fig. 163 is a diagram illustrating the electrical 
contact in a central incisor. A is the orifice of the opening 
into the pulp chamber which lias been enlarged internally, as 
indicated by the dotted line C, into which is placed the + 
platinum electrode. B is a small drill hole in which is placed 
the — platinum electrode. D is a small opening made between 



ELECTROLYTIC TOOTH BLEACHING 307 

A and B to complete liquid contact and thereby reduce 
resistance effects. If the tooth is filled or decayed at an ap- 
proximal surface this position should be utilized for introduc- 
ing the second electrode (as shown in Fig. 164). Into the 
cavity, between the metallic conductors, should be placed a 
pellet of cotton-wool in the meshes of which has been incorpo- 
rated a pasty mixture of chlorinated lime, and 2 per cent, 
sodium sulphate. The circuit should be established by 
gradually turning on the current until 5 ma. are measured 
on the milliamperemeter. By the electrolytic action nascent 
oxygen is eliminated at the positive pole and hydrogen and 
chlorine at the negative at the same time electrolysis of 
water takes place; H 2 molecules accumulate at the negative 
and O at the positive electrode. The chemical action which 
takes place by the passing of the current furnishes a large 
supply of nascent oxygen, chlorine, and hydrogen. The 
chlorine has a great affinity for hydrogen, with which it 
combines freely. The positively charged atoms H 2 + Cl 2 
migrate to the negative pole, where they give up their charge 
of electricity to the electrode and unite to form 2HC1 (hydro- 
chloric acid), the negatively charged atom O migrates to the 
positive electrode, where it unloads its charge of electricity 
and O is eliminated. By this means a large quantity of oxygen 
is liberated in contact with the dentinal tubuli, the hydrogen 
which would unite with it to form water is utilized by the 
chlorine atom which leaves the nascent oxygen free to com- 
bine with organic matter in the tubuli of the dentine. 

The action of these gases is hastened and increased by the 
evolution of heat which takes place during the passing of 
the current, the electrodes which should be thin platinum 
wire (0.5 mm. diameter respectively) become heated when 
the electro-motive force is about 20 volts, passing a current of 
about 5 ma. This heating effect can be increased by either 
diminishing the size of one electrode or by increasing the 
E. M. F. to 30 volts, passing 10 ma. By this means the tooth 
structure can be heated considerably, which assists the 
bleaching effect by increasing oxidation. 

When bleaching is almost completed in the body of the 



308 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 

tooth a fresh supply of bleaching mixture should be placed 
in the tooth and the poles of the battery or switchboard 
reversed to complete the process about that part which 
formerly contained the negative electrode. 

It will be noticed that during the bleaching operation 
by this method very little chlorine gas escapes, and the 
odor of chlorine is very faint. This is most likely due to 
the perfect union of Cl 2 + H 2 in the formation of 2HC1; 
on the other hand, if a weak solution of sulphuric acid be 
used as the solution electrode with chlorinated lime, the 
pungent odor of chlorine gas is distinctly observed. 

The canals of all teeth which are bleached with chlorin- 
ated lime should be previously sealed at their apices with 
gutta-percha. There are some precautions which should be 
observed when electrodes approximate each other so closely 
as here described. The wires should be properly insulated to 
prevent short circuiting; the solution electrode in the tooth 
should be replenished when necessary; if it become dry the 
resistance to current is much increased and heat is increased; 
one electrode should be made fast in the tooth by some 
mechanical contrivance, and should be made secure in posi- 
ition before attaching the conducting wire to it, if it is bent 
into a hook at the end as shown in the diagram (Fig. 164) 
the conducting wire can be readily attached; the operator 
should control the other electrode. After bleaching, all traces 
of the products of electrolysis and the bleaching agent should 
be removed, and the cavity wiped out with a solution of 
bicarbonate of soda or ammonia water. 

Bleaching with Hydrogen Dioxide. — The bleaching with 
hydrogen dioxide, sodium dioxide, and pyrozone with the 
electric current are so similar in chemical action and effect 
that all can be described under the same heading. 

In the case of sodium dioxide the migration of sodium 
ions (which are colorless) takes place at the + pole. 

The method of applying both electrodes to the tooth 
already described is very effective in the use of H 2 2 prepara- 
tions. The current strength necessary to eliminate oxygen 
gas by this technic is reduced to a minimum and the resist- 



NEURALGIA 309 

ance of the body in circuit is eliminated: moreover, heat 
can be produced in the tooth without discomfort, which is 
a valuable auxiliary. 

The H2O2 solution should be placed in the cavity on 
cotton-wool between the electrodes; on passing the current 
large quantities of gas is evolved at both electrodes: the 
H atoms migrate to the negative electrode and to the 
positive. Alter operating with the current passing in one 
direction for five to eight minutes the poles should be 
reversed and current passed in the opposite direction for a 
similar time. In addition to liberating the very loosely 
combined oxygen atom in H-O? solution, electrolysis of ILO 
takes place, which supplies a further atom of nascent oxygen 
for action on organic matter in the dentine. In teeth of 
young subjects and recently discolored teeth the electrolytic 
bleaching action of the H0O2 is very rapid. 

To facilitate electrical conduction in ITO? preparations. 
the addition of 10 parts in 100 of 2 per cent, solution of 
sodhun chloride or sulphate should be made: and in the 
case of ethereal solution of pyr ozone the ether should be 
evaporated over a hot-water bath after adding a similar 
volume of 2 per cent, sodium sidphate. 



NEURALGIA. 

The term neuralgia is applied to a painful affection of 
either the course of a nerve or the area of its distributions. 
It is a condition of pain, which in the early stages may 
amount to mere flashes of pain, responding to some afferent 
impulse set up by an irritant in a remote part, but later a 
more lasting and severe pain results in consequence of con- 
tinual irritation of the nerves responsible for the reflex 
action. Trifacial or trigeminal neuralgia which occurs in 
connection with the fifth nerve is constantly brought to our 
notice in its many phases. Diagnosis of the cause of facial 
neuralgia when the teeth are responsible for the irritation 
setting up this reflected pain in one of the facial segmented 



310 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 

areas is often difficult, but much is done by the dentist in his 
daily practice to arrest and relieve this form of pain. Never- 
theless, obscure cases arise which defy the skill of the medical 
and dental professions, especially that form of neuralgia 
known as tic douloureux, which is not ordinary "referred 
neuralgia" but is often regarded as a diseased state of the 
Gasserian ganglion or a large branch of the fifth nerve. 

Facial neuralgia is often caused from septic periodontitis 
and indirectly from the effects of this disease; the sensitive 
necks of teeth are exposed to the irritating influences of 
external agents which provide constant and more or less 
severe afferent stimuli to be sent out from the surfaces of the 
teeth, these sensitive surfaces are peripheral endings of the 
fifth nerve, which are exposed and convey painful impulses 
to the nerve trunk or Gasserian ganglion, resulting in reflex 
neuralgia. This form of reflected pain is exceedingly common 
among patients suffering from pyorrhea alveolaris, and the 
question of treating the disease should include the possibility 
of relieving this phase. It is often the case that acute 
neuralgia follows the operation of scaling the teeth, and 
many patients suffer from constant facial neuralgia who have 
so-called "dry pyorrhea." 

The author has noticed with considerable satisfaction 
the remarkable effect on neuralgia which is caused from sen- 
sitive surfaces of teeth by their treatment with zinc ions. 
Many cases of persistent and long-standing neuralgia in 
the maxillary, temporal, frontotemporal, and mandibular 
areas have completely disappeared after treatment of 
pyorrhea with zinc ions and silver ions. In the treatment 
of these cases the application of the current at first causes 
neuralgic pains in the reflected area from which the patient 
generally suffers or corresponding to the area influenced by 
the particular teeth to which the current is applied, and it is 
often impossible to apply more than a very weak current, 
0.5 or 1 ma., but when the pyorrhea is cured, at subsequent 
treatments it is the experience of the writer that the sensitive- 
ness of the exposed necks of teeth has become less, the neuralgia 
is relieved, and teeth which were formerly painful when 1 ma. 



NEURALGIA 311 

current was applied are painless with 3 or 4 ma. The relief to 
neuralgia is usually very prompt, although the relief to the 
sensitive surface of the teeth is slow and may not be complete, 
so far as passing current is concerned, for several years, but 
the ultimate effect in this respect is sure and most noticeable 
from a clinical stand-point. 

In the treatment of exposed roots of molars, especially 
in the palatal aspect of maxillary and approximal surfaces 
of mandibular molars, the application of silver ions from a 
weak aqueous solution of silver nitrate is very rapid in 
removing sensation from these surfaces and the effect is 
permanent. 

The only construction that can be placed on the action 
of the ion in this respect is that it passes into the organic 
structure of the dentine and cementum by conduction, 
the penetration is into the protoplasm of the cell, where 
the effect of the ion is far more complete than if the drug 
were applied as tincture or liniment painted on the surface; 
the action in the latter case is only superficial and pene- 
tration at the best very imperfect. When we consider that 
by the electrolytic effect the molecules are split and the 
ions are conveyed by the electrical charges along a definite 
path of conduction, which, in so dense a structure as dentine, 
provides no means of circulatory absorption of the disso- 
ciated salt, the medicamental effect, if produced at all, must 
be of a lasting nature. Chloride of zinc and silver nitrate 
as metallic salts in solution have long been known to have 
obtunding effects on sensitive dentine, but much of the good 
effects are lost in ordinary applications for the lack of pene- 
tration. With electrical application we are provided with 
just that which is lacking to obtain the desired effect. 

Septic infection of the oral cavity is accounted by some 
authors to be the principal cause of facial neuralgia arising 
from fifth-nerve reflexes, and it can be readily conceived 
that constant afferent impulses directed to the nerve centres 
from the seat of such general irritation, accompanied by the 
general constitutional depression and lowering of the tone 
of the system by absorption of septic matter, would be the 



312 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 

cause of nerve excitability and even disease of nerve centres 
directly connected 

But the sensitive condition of soft tissues in periodontal 
disease is not as frequently the irritant responsible for 
reflected pain as is the sensitive surface of the teeth them- 
selves, which are liable to cause reflex pain from influences 
that do not affect the soft tissues, such as thermal changes, 
sweets, or sours. 

In treating sensitive pyorrhea teeth a flat zinc electrode 
of large enough area to cover the whole surface of a man- 
dibular incisor should be wrapped with cotton-wool which 
is saturated with 3 per cent, zinc chloride warmed to 99° 
Fahrenheit, the electrode should be firmly pressed to the 
surface of the tooth and the current turned on very grad- 
ually until felt by the patient; by keeping it steady it is 
often possible to use more current, the current should be 
turned off slowly after a few minutes and the operation 
repeated on another tooth. These teeth are very sus- 
ceptible to shock from sudden alteration of the E. M. F. 
and great care is necessary in using the current. Perio- 
dontal and gum tissue can be treated at the same time by 
passing the point of the electrode under the gum; the 
number of treatments and the time occupied correspond 
with the method of treating septic periodontitis already 
described. 

Neuralgic pain referred to in connection with periodontal 
disease is usually slight and transient, but occurs frequently 
and is the cause of much discomfort to the patient, who will 
complain of it. A more severe form of facial neuralgia which 
is probably developed from long standing and everlasting 
repetition of the slighter form is well known to the medical 
world. The sufferings of the patients in these cases are intense 
and the medical man is usually consulted. The electrical 
treatment of these cases has met with considerable success. 
The principle of counter-irritation is carried out with a con- 
tinuous current applied with electrodes of large area and a 
current of considerable intensity. The active electrode is 
applied to the whole surface of one side of the face in close 



NEURALGIA 313 

contact with the skin, it is E-shaped, which leaves apertures 
for eye and month. The indifferent electrode, also of large 
area, is placed at the back of the neck. A current of 30 to 
80 ma. is passed for half an hour at a time every day or 
every other day, diminishing the current as the neuralgic 
symptoms become less. Good results are claimed for this 
method of treatment when the neuralgia is of local origin. 
Lednc 1 has reported the successful use of salicylic and 
quinine ions introduced electrically by much the same 
technic as just described. The method is quite new but 
the results already obtained in severe trigeminal neuralgia 
should lead to its general use in these cases, especially 
when other forms of treatment have failed. Dr. R. W. 
Mackenna reported a case of immediate relief of neuralgia 
by the use of salicylic ions with a comparatively low current. 
He says: "I have had remarkable proof of the efficacy of 
the salicylic ion in the treatment of neuralgia following 
herpes. The patient had not slept for four nights because of 
the intense pain, but found relief after the ions from a 2 per 
cent, solution of salicylate of soda had been carried into the 
affected zone by a current of 7 to 11 ma. for thirty minutes. 
She was able to sleep immediately afterward, and when next 
seen had had no return of pain." 

In cases of neuralgia of the trigeminus dependent on 
some form of peripheral irritation, where the nerve trunk 
in its passage through bony canals is not affected by disease 
of those parts or by pressure from tumors in its vicinity, a 
form of electrical treatment has been recommended by many 
which is not dependent on influence of ions introduced sub- 
cut aneously, but on the counter-irritation effect of a weak 
current applied to the painful area. By this method a con- 
tinuous current of 3 to 5 ma. is passed for five to ten minutes 
with the anode of a surface area of about 6 sq. cm. applied 
to the points of emergence of the branches of the nerve, 
the cathode is attached over the upper cervical vertebra? 
and has an area of about 100 sq. cm. The electrodes must 

1 Archives d'Electricite Med., July 25, 1904. 



314 ELECTRICITY FOR ANESTHESIA AND NEURALGIA 

be firmly applied, care being taken to avoid interruptions in 
the circuit. The results of this form of treatment of facial 
neuralgia is sometimes very effective and most gratifying, 
relief being obtained by one daily treatment, and if pain 
recurs the application promptly relieves it. 

Lewis Jones 1 says of trigeminal neuralgia, a In this con- 
dition, in particular, the salicylic ion has yielded most 
satisfactory results, and successful cases have been recorded 
by numerous writers." The application is made by placing 
a folded cloth pad over the whole area of the face, on this 
securely bandage the feet-covered electrode, the pad is 
moistened with a hot solution of sodium salicylate, 2 per 
cent. The indifferent electrode is placed upon the chest or 
under the shoulders. Care must be taken that all binding 
screws and conducting cords are securely fastened and in 
good condition. A current of 30 ma. or more is applied 
for half an hour, and repeated every second day for the first 
week and every third day after. The salicylic ion is an anion, 
it is therefore applied at the negative pole. The current 
should be turned on and off very gradually. Good results 
are so often reported from this method of treating trigeminal 
neuralgia, that it certainly should be tried in difficult cases, 
especially when other local treatment fails. 

1 Ionic Medication, p. 102. 



INDEX. 



Abbot, C. H., on x-rays, 167 
Abscess, 157, 268, 27l" 
Absorption of roots and bone, 174, 

176 
Accumulators, 61, 128 

battery, 62 

for cautery, 97, 128 

charging, 62 

for dental engine, 64 

Edison's, 64 

for mouth lamps, 128 
Active electrode, 109, 251 
Adrenalin ion, 246 
Advantages of ionic medication, 247 
Alternating current, 88 

transformer, 89 
Alto-frequent current, 257 
Alveolar abscess, 179, 268 

chronic, 271 
Ammeter, 102 
Ampere, 35 
Ampere-hour, 62 
Amperemeter, 102 
Anesthesia of dentine, 218, 300 

of gums, 305 

of pulp, 246, 303 
Anesthetic effect of high-frequency, 

256 
Anion, 46 
Anode, 46 
Antrum, 159 

perforation of, 160, 193 

troubles of, 191, 192, 193 
Arrangement of cells, 67 



Bacteria, effects of ions on, 247 
Battery, 92 



Battery accessories, 98 

accumulator, 97 

cautery, 96 

Edison storage, 64 

home-made, 94 

Leclanche dry cell, 93 

secondary, 61 
Bauer qualimeter, 150, 152 

tubes, 147 
Beez scale, 150 
Benoist scale, 150 
Bichromate cell, 57 
Bleaching, electrical, 253, 305 
Breaks, 143 
Bucky, Dr. G., 168 



Capacity of Leyden jar, 22, 36 
Caries under crowns and caps, 191 
Cataphoresis, 213, 218 
Cataphoric effect, 213, 219 
Cautery, accumulators for, 97 

batten', 97 

switchboards for, 115, 130 
Cells, 30, 53 

bichromate of potash, 56 

Bunsen, 58 

Daniell, 59 

Grove, 59 

Leclanche dry, 55 
wet, 53 

in multiple arc, 71 

in parallel, 70 

persulphate of mercury, 57 

in series, 67 

Smee, 56 
C. G. S. system, 34 
Charging accumulators, 62 
Chemical equivalents, 46 
Chin electrode, 109 



316 



INDEX 



Chronic alveolar abscess, 271 
Cieszynski, 149 
Clark, Mr. C. E., 137, 296 
Cocaine anesthesia, 219 

toxic effect of, 210 
Coil, induction, 81 

secondary, 83, 85 
Collectors, 98 
Colyer, J. F., 238, 273 
Commutator, 85 
Condensers, 118 
Conduction, 22 

by ions, 46, 204 
Coolidge tube, 150 
Coulomb, 35 
Creasey, L. C, 255 
Cryer, 149 

Cryptoradiometer, 150 
Cryptoscope, 151 
Current, 25, 28, 77, 79, 82 

alternating, 88 

conducting cord, 105 

continuous, 85 

converter, 127 

effects on nutrition, 225 
on salivary glands, 226 

from main, 85 

heating effects of, 38 

interrupted, 85 

measurement of, 33 

reverser, 92 

unit of strength, 35 
Cysts, 157, 183 

radicular, 183 



Danger of x-rays to patient, 166 

to operator, 167 
Daniell cell, 59 
d'Arsonval, 40, 117 
Density, 72 

Dental electrical appliances, 123 
Dentine obtunding, 300 
Dessauer coil, 158 
Development of radiographs, 202 
Dieck, 149, 151, 155, 198 
Diffusion of current, 222 
Dissociation of molecules, 47 
Double collector, 100 
Dry cell battery, Leclanche's, 92 



Dry pyorrhea, 278 
Dunn, Dr. Wm, 256 
Dynamo currents, 85 
plan of, 86 

E 

Edison accumulator, 64 
Effects of current on nutrition, 225 
on salivary glands, 226 

of ions on bacteria, 247 
Electric diffusion, 218 

engine, 124 

furnace, 134 

gold annealer, 136 

lathe, 126 

machine, 26 

osmosis, 214 

sterilizer, 133 

syringe, 132 
Electricity, galvanic, 28 

static, 17 

theories of, 17 
Electrodes, 205 

active, 109, 251 

carbon and water, 108 

chin, 109 

copper, 110 

for fistula, 111 

hand, 108 

high-frequency, 122 

indifferent, 106, 252 

iridioplatinum, 253 

platinum, 110, 253 

pyorrhoea, 110 

root-canal, 110 

vacuum, 122 

wrist, 106 
Electrolysis, 43 

of living tissue, 220 
Electrolyte, 30 
Electrolytic effects, 220 

tooth bleaching, 305 
Electro-magnet, 76 
Electro-magnetic field, 75 

induction, 77 
Electro-motive force, 31 
Electrons, 20 

Electro-physiological effects, 203 
Electro-positive and negative, 50 
Electroscope, 20 
Empyema, 192, 193 



INDEX 



317 



Equivalents, chemical, 46 
Experiments, 206, 208 
cataphoric, 215, 216 
ionic, 207, 208, 209 
Exposure, time of, 161 
Extirpation of pulp, 304 



Farad, 34 
Faraday's law, 45 
Faradization, general, 225 
Film holder, 175 
Bauer's, 175 

interpretation, 158 

wrapping, 166 
Finzi, S. N., 208, 303 
Fluorescent screens, 161 
Foot warmer, 133 
Foreign bodies, location of, 198 
Fractures of jaws, 197 
Frictional electricity, 17, 25 
Furnace, electric, 134 



Galvanic battery, 93 

electricity, 28 
Galvano-cautery, 96 
Galvanometer, 100 
Gingival trough^ 279 
Gingivitis, 275 
Glands, treatment of, 255 
Gold annealer, 136 

cyanide, 49 
Gouty diathesis, 284 
Granuloma, 180 
Graphite rheostat, 103 
Grove's cell, 59 
Guilleminot, 48, 226 
Gums, anesthesia of, 305 
Gunshot lesions, 197 



Hand electrode, 108, 252 
Heating effects of current, 38 
High-frequency apparatus, 117 
currents, 116, 255 



Holtz machine, 25 
Hot-air syringe, 132 
Hot-wire ammeter, 121 
Human body resistance, 226 
Hydrogen dioxide bleaching, 308 



Immediate extirpation of pulp, 304 
Impacted teeth, detection of, 172, 

173 
Incandescent lamps, 63, 255 
Induced currents, 77 
Induction, 19, 24, 77 

battery, 85 

coil, 81 

self-, 80 
Insulators, 23 

Intensifying screen, 161, 162 
Intensive irradiation, 255 
Internal resistance, 37 
Interpretation of films or plates, 
157, 158, 159 
mistakes in, 159, 160 
Interrupters, 143 
Ionic medication, 204, 232, 247 
Ions, 46, 204 

adrenalin, 246 

cocaine, 245 

copper, 207, 244 

ferrous, 207 

iodine, 245 

salicylic, 235, 246 

silver, 245 

zinc, 234, 244 
Iron, 30, 37 



Jack, Dr. Louis, 303 
Jar, Ley den, 22, 118 
Jaws, necrosis of, 196, 273 
Jones, Lewis, on cataphoresis, 217 

on ionic medication, 234 

on ions, 204 

on path of current, 221 

on resistance, 229 
Joub's law, 39 



Kathode, 46, 205 
Kations, 46, 205 



318 



INDEX 



Kells, 163 

Kirk on bleaching, 305 



Lamp, mouth, 132 

Lange, Sidney, 149 

Lead accumulator plates, 61 

Leclanche cell, 53 

Leduc S., on cocaine, 246 
on dissociation of ions, 47 
on ionic medication, 313 

Leyden jar, 22, 118 

Lime, chlorinated, 306 

Lines of force, 74 

Lodge, Sir Oliver, 20, 76 

Lupus, 234 

Lymphadenitis, 255 

M 

McCoy, 149 
McGraw, 218 
Magnet, 74, 75, 76 
Magnetic field, 74, 75, 78 

force, 74, 75, 78 
Mains, current from, 85 

switchboard for, 113, 126 
Marginal gingivitis, 275 
Marie, 163 
Measurement of current, 33 

of resistance, 150, 227 

of root (x-ray), 174 
Milliamperemeter, 100, 121 
Mitchell, William, 167 
Monkey, experiment on, 208 
Morton, W. J., 51, 215, 218, 232 
Motor converter, 130 

dynamo, 88 

transformer, 119 
Motors, 123 
Mouth lamp, 132 

wash, 290, 291 
Miiller tubes, 147 
Multiple arc connection, 71 



N 

Necrosis, 196, 273 
Negative electricity, 19 



Nerves, motor, 222 

sensory, 223 

special, 224 
Neuralgia, 194, 235, 309 
Nutrition, effects of current on, 225 



Ohm, 34 

Ohm's law, 33, 38 

Olfactory nerve stimulation, 225 

Optic nerve stimulation, 225 

Oral sepsis, 278 

Orthodontia, 170 

Osmosis, 214 

Ottolengui, 155, 198 

Oxygen in bleaching, 306 

Ozone, 258 



Parallel, cells in, 76 
Parker, Dr. C. H., 259 
Path of current in body, 221 
Peckert, 149 
Penetration of ions, 205 
Perforation of root, 272 
Periodontal disease, 277, 283, 288 
Periodontitis, 266 

acute local, 267 
Persulphate of mercury cell, 57 
Pfahler, 149, 196 
"Phantom" skull, Dieck's, 166 
Physiological effects of current, 214 
Plate holder, x-ray, 166 
Plates of accumulators, 61, 65 
Platinum electrode, 110, 253 
Polarization, 40 
Poles, testing of, 42 
Port, 149 
Potential, 29, 32 
Practical electrical units, 34 
Price, 149 

Primary current, 141 
Prinz, 264 

Protective materials, 167 
Pulp anesthesia, 303 

immediate extirpation of, 304 

septic, 262 

stones, 190 



INDEX 



319 



Pus, periodontal, 288 

Pyorrhea alveolaris, 186, 188, 277 
diagnosis of, 278 
treatment of, 277-299 
dry, 283 

Q 

Quallmeter, Bauer's, 150, 152 
Quantity of electricity, 35 
Quinine ions, 313 



R 

Radiodontta, 159 

Radiographs, development of, 204 

Radiography, 148 

Raper, 149 

Ravs, direction of, 153, 154, 157, 

181, 201 
Referred pains, 310 
Resistance, 36 

of body, 226 

of dead teeth, 230 

of dentine, 229, 253 

for heavy currents, 114, 126 

heating effects of, 38, 254, 307 

instruments, 114, 127 

internal and external, 37, 68 

of lamps, 63 

measurement of, 150, 227 

of metals, 37 

Ohm's law of, 37, 68 

of tubes, 149, 150 
Resonator, 118 
Rhein, 149 
Rheophores, 105 
Rheostats, 102 

for direct current, 111 
Ribault, 163 
Rodent ulcer, 234 
Rollins, 149 
Rontgen rays, 137 
Root canals, treatment of, 262 

measurement (Ottolengui), 155, 
198 

sterilization, 264 



Salicylic ions, 235, 246, 313 
Salivary glands, 226 



Scale, Walter, 150 

Wehnelt, 150 
Screen, fluorescent, 161 
Secondary batteries, 61, 128 

coil, 82 

rc-rays, 168 
Self-induction, 80 
Sensitive dentine, 300 
Sensory nerve effects, 223 
Septic infection of periodontal 
membrane, 283 

periodontitis, 266 
^ pulp, 262, 266 
Series-wound dynamo, 87 
Shenton, 149 

Shunt-wound dynamo, 87 
Siemen's coil, 158 
Silver ions, 245 
Smee cell, 56 

Smith, Hopewell-, 280, 293 
Snook Rontgen apparatus, 140 
Sodium ion, 52 
Spark gap, 118 
Special nerve effects, 224 
Static electricity, 25 

machine, 25 

wave currents, 255 
Stereoscopic radiography, 162 
Sterilizers, 133 
Storage battery, 61, 64 
Switchboards, for battery, 95 

dental, 126 

for ionic medication, 113 

resistance, 112 



Technic of dental radiography, 
148 
of ionic medication, 250 

Teeth, bleaching of, 253, 305 
gingivitis about necks of, 275 
perforation of roots, 273 
removal of calculus from, 277 
resistance to current, 222, 230, 

253 
sensitive necks of, 286 
septic infection, 266 
treatment of dead, 262 

Testing the poles, 42 



320 



INDEX 



Theories of electricity, 19 
Therapeutic effect of current, 231 
Thomas, 180 

Tousey, 149, 167, 175, 259 
Toxic effect of cocaine, 210 
Transformers, 89 

alternating current, 115 

for cautery, 91 

for high-frequency, 91, 119 

motor, 116 
Traumatic lesions, 185, 190 
Trismus, from impacted molar, 269 
Tumors, 196, 197 
Turner, Dawson, 229, 235, 247 



U 



Units, practical electrical, 34 
Uric acid diathesis, 284 
Use of x-rays, 170 



Vacuum electrodes, 122 

Van Woert, 149 

Volt, 35 

Voltmeter, 102 

Volta's contact law, 29, 51 

Voltaic cell, 31, 53 



W 

Walter scale, 150 

Water electrode, 108 

Watt, 36 

Weski, 149 

Wehnelt cryptoradiometer, 151 



Williams, 149 

Wimshurst's machine, 26, 141 

Wire rheostat, 104 



X-ray apparatus, 137 
diagnosis, 170 
of abscess, 179 
of antral disease, 191 
of broken instrument, 189 
of calculus, 186 
of carcinoma, 197 
of cyst, 183 
of exostosis, 195 
of fracture of jaw, 197 
of necrosis, 196 
of pulp stone, 190 
of pyorrhea, 186 
of root absorption, 176 
filling, 198 
fracture, 189 
length, 198 
of sarcoma, 197 
tubes, 147, 150, 260 
of tumors, 196 
of unerupted teeth, 171, 194 
X-rays and high-frequency, 258 
dangers to operator, 166 
exposure, time of, 161 
extra-oral, 165 



Zinc, 30, 52 
electrodes, 110 
ions, 234, 244 

Zierler, 249, 264 



